Musiland Monitor 02 US - Reviews
Pros: Robust design and transparent to use
Cons: No BNC connector support
the device complements nicely Matrix mini DAC to support 192k signal through USB connection.
SQ is good, and when it is connected it instantly is recognized.
Housing is aluminum and strong. Power connection is made directly to AC without any hassles about the DC converting block.
Pros: Great tone, no colorization, rich mids , timbre and bass impact
Cons: Front RCA output = messy wiring, should have been put in the rear
Features (listed from coolfungadgets)
•High speed USB connection
•Independent power module provides pure and strong power supply
•Independent APU MU6010 for 24 bit/192kHz audio processing
•High quality S/PDIF transmitter
•Optical toslink & coaxial RCA digital output
•Stereo RCA, 3.5mm headphone analog output
•Headphone 1 is for medium/high resistance headphones
•Headphone 2 is for low resistance headphones
•Support 24bit/192kHz digital output
•Specialized ASIO driver - support Windows XP, Windows Vista and Windows 7
•Aluminum alloy chassis for minimum interference

I have been using my X-Fi for 3 or 4 years now. I've also upgraded the opamps to LM4562 (improved high end details and transparency over onboard sound, less edgy but vocals still sounded a bit "digitalized" if you get me) and decoupled the capacitors for about 2 years now. The 02 US sounds like an improvement far greater than the jump from onboard sound to a modded X-Fi, to me it really felt like the next step.

I don't really feel like there's any point in comparing my onboard realtek "high definition" audio as it's fairly low end (harsh, lack of resolution and dry) such that my zune and sansa clip sound better (greater dynamics , greater soundstage and generally more detailed)

I mainly listen to rock,alternative,classic,electronic,piano pieces and once in a while pop just for the heck of it
It has a very solid casing, very study and not made of thin metal.
Sound comparison
02US vs opamp upgraded X-Fi Xtrememusic

Headphone used : Grado SR-225 (X-Fi cannot drive my HD580 adequately, sounds quite anemic I should say)
No dedicated amp was used

Speakers : M-Audio BX5a

The first thing apparent between the two is the instrument decay and texture. For the X-Fi I can't distinguish timbre well at all , the 02US really fleshes it out for a violin,saxophone,flute,clarinet and piano for example. As I know, it is not only the pitch or tone that makes me able to distinguish an instrument, it's much of the texture. The X-Fi has wide soundstage compared to onboard, however the depth is further improved on the 02US as well as the width ( the depth was a more noticeable change than width). Instruments have a more apparent occupation in space; X-Fi sounds cluttered in comparison. The vocals on the 02US are great, and sound natural without a hint of edginess or graininess. The X-Fi presentation of vocals ( can be smooth and rough at times) vary through a variety of recordings but the 02 US manages to keep its smooth vocal characteristic a constant. I didn't notice anything too different about the distance of vocals between the two sources. Everything sounds so well together, the layers of instruments and vocals blend in together well without losing any detail and does not become a mess. It is really a bliss listening to vocals on the 02US unlike any other sources I have

The 02US is able to be very detailed (again the decay and timbre is beyond the X-Fi) and crisp in even complex passages where the X-Fi loses midrange detail and separation creating a small mess. Like many source upgrades, I find myself hearing new details and for details that were already there, stood out even more. The separation in the strumming of an acoustic guitar for example is good on the X-Fi but 02US manages to bring out even more distinction between each pluck. Also passages of music pieces when the choir comes in, the 02US makes it noticeable there are more singers there with the choir; the X-Fi makes it seem as if the choir is short a few voices. The 02US is easily able to dissect small details and present them, where the X-Fi isn't able to discern them at all.

The 02US is able to keep its composure of sounding smooth, detailed and transparent at all times. Although the 02US is smooth sounding, it is capable of making guitars in rock sound lively. Drums have a dynamic snap and cymbals actually shimmer. Pianos notes have body, tone and decay not distinctively apparent on the X-Fi. I can't stress how smooth flowing the sound is compared to the X-Fi, it really needs to be heard than described. It does so without being mellow,boring,overly gentle or lacking in dynamics, and has rhythm. I can even listen to the 02US at a slightly higher volume because of how non-fatiguing it sounds.

Regarding the highs, I have always wanted more out of the X-Fi despite the improvement by replacing the opamps. It didn't have that sparkle and is tad shrill. 02US remedied this for me, violins really "sing" and something like a triangle instrument had the sparkle on its initial hit. Lastly, the low end frequencies on both are comparable but in terms of impact the 02US has the edge creating greater dynamics which is nice for kick drums for one. Bass in some songs had a tighter and more controlled punch to it compared to my X-Fi which is more loose.

If I had to pick a word to roughly sum up both sources

X-Fi : Artificial
02US : Natural
Musiland 02US is competitive to the uDac. Musiland 02US has slightly more forward vocals, more extended high and better bass impact and depth. This comparison was made through my Arietta amp
02US is one of the best value DACs I have owned. Those with harder to drive cans may want to pair this up with a proper amplifier.
So thanks for these reviews they were great to get an idea of what kind of DAC the Musiland Monitor 02 is, and I am currently out of work but slow saving through odd jobs for one, because they seem to be priced well considering what you get as far sound quality, stage, and as far as it seems a more natural clarity. I am newer to the community and have a high end system with high end keyboards, parts, etc. Well my audio was a serious bottle neck and at the time I had stopped listening to music but now I have found passion in my life again and have done well considering the money budget. I am using DT990s and soundMagic HP100's. 
Pros: Async, 24/192, Low-jitter transport
Cons: Windows only, drivers can be a pain depending on computer and OS, weak built-in Headphone amp
If you are looking for for a cheap Async DAC that does a lot for $150 then look no further than the Musiland Monitor 02 US. 
Unlike many DACs in the market this DAC focus on Computer Audio only (which is great for me since I don't need Toslink or Coax inputs).   Using Async USB the DAC delivers Hi-Fi sound performance, but I do have to question why Musiland have to use a lower-end Op-amp in the analog stage?  I'm thinking because of the lower-end Op-amp the DAC is not delivering up to 100% in my opinion. 
Because of Async this DAC for the price supports 24/192 files, but honestly most of my digital music is the redbook standard so the hi-rez doesn't get used often.  I listen to 24/176.4 files on this before (Reference Recordings HRx stuff) and I found the DAC to do a great job with those. 
If you decide that you want to use the Monitor 02 US as a digital transport you can.  With the Monitor 02 US using its own power source it will do a better job as a digital transport than the Monitor 01 US (which uses USB power which IMO should be avoided at all cost when it comes to audio).  It has Toslink and Coax outputs if you were wondering.  I prefer one-box DACs so I don't want to use the Monitor 02 US as a digital transport (but you can if you want). 
I think the issue people could see with this DAC that it is Windows only because of its drivers.  Also the drivers did cause issues on peoples computers (I heard that it was giving problems with Windows 7 computers with AMD processors, I had this problem before). 
Also by looking at the picture of the product it does have two headphone jacks.  Headphone jack 1 is for high impedance cans while 2 is for low impedance.  With my experience with the headphone jacks I would recommend to avoid them at all cost.  These headphone amps just don't cut it IMO with my Grados for example.  If you are getting this DAC you better get an external amp for your cans.
Overall with some issues this is a good value DAC for people who want to get into Hi-Fi without breaking the bank. 
Note:  I would say the drivers are adding in new features and now this DAC can decode HDCD (via driver software) and have a special precision mode so the internal clocks will be close to its perspective sampling rates.