I bought these headphones a little over a week ago, and thought I should post my impressions. I work in a small office, and sit close to my boss, who is constantly on the phone, so I wanted a noice-canceling big headphone for home and for the office. I first listened to these a year ago and fell in love with the sound, but my wallet didn't allow the purchase, and now I own them, and am very happy with them.
 
Previously I owned the K701's, but sold them because the headband hurt my scalp, and I've been using in-ear phones since. I mostly liked the sound in the K701; the bass was very correct, but sometimes not that fun, and the highs were incredibly unforgiving. The PSB's are more balanced in my view, and have a bit more oomph, especially with the built in amp on. The noice canceling works well in the office, but does change the sound slightly, I can't put my finger on what happens, but it is not as good as with just the amplification on. Either having a stack of batteries handy or a charger seems to be needed, but I think this is a better solution than a built in charger.
 
Edit: Formatting

Background
I've had the JCV Victor FX500 / FX1000 earphones for several years now, and been very happy with the sound. The plug is now hanging on by a thread and I wanted something new before it breaks. After a bit of research I found out that XTZ, a company from my own country, had developed an earphone with DSP correction for the iPhone. There are two versions of these earphones, the EarPhone 12, which is just the phones, and EarPhone 12 Sports, which has an in-line mic, ear hooks and a clothes clip. The one thing I had been missing with the JCVs was a mic so I chose the Sports.
 
Design
The housing, though it looks like metal, is made of durable plastic, something I think is good since it keeps the weight down. They are quite big for in-ear phones but fit comfortably nonetheless, and the ear hooks attach and detach easily. The combination of the gunmetal gray housing and the black and red narrow but flat tangle free wire is cool and sporty. There are magnets in the back of the earphones that makes them attach like a necklace while not in use, something I found pretty useful.
 
The Sound
The sound out of the box was pretty damn good for an earphone in this price range, but when I installed the XTZ Player and turned on the Dirac DSP correction, Just WOW. The soundstage opened way up, the clarity in the bass and highs improved greatly, and it just put a smile on my face. There are 6 different corrections, the standard, 3 bass boost modes, a Bright mode and one for when you use ComplyFoam buds. The bass boost is very well done and doesn't detract from the detail in the sound, and is perfect to use when listening to older rock or other music that can be a bit thin. I haven't seen much use of the Bright option, since I like the level and clarity of the highs a lot, but for some recordings it is appropriate.
 
Compared to JVC
Without the corrections on the JVC phones does sound a bit better, as they should, being almost 3 times as expensive, but once the DSP is on the XTZ:s even surpasses them. They isolate much better, and the cable means they tangle less. The sound is a bit more linear, and the bass is great on both but even better on the XTZ.
 
I recommend these earphones wholeheartedly, and I can see myself replacing the JVCs with them full time.

Note: I'm from Sweden so if the wording or sentence structure is a bit off, I blame the Swedish educational system!! 
 
Introduction
The ASUS Xonar Essence STX is a two channel soundcard with a built in amplifier and it is a great entry into hi-fi and head-fi, it has a good set of features and handles most games very well, at least with the newer drivers. The card has a good DAC-chip that leads into two I/V stage Op-Amps and then on to either the headphone amplifier chip, called a Hi-Z amplifier, or to the buffer stage Op-Amp. There is also a decent mic/line in for recording. The card takes its power directly from the PSU and therefore gets a very clean and strong power supply, at least if the PSU is good. The software has pretty good features and the interface is pretty self-explanatory for the most part.
 
Op-Amps
After getting this card I started reading the already massive thread started by ROBSCIX on this site, and soon enough I wanted to try to see what this card really could do. The sound with original chip Op-Amps was somewhat on the warm side and lacks a little something in detail but it is a good sound non the less. After reading 70+ pages of the gargantuan thread I came to the decision that the greatest improvement would come from upgrading to discreet Op-Amps from Audio-GD. After consulting some reviews and exchanging a few PMs with ROBSCIX I decided on OPA Earth for I/V and OPA Sun for buffer. This improved the sound through my loudspeakers with better positioning, better bass quality and clearer transients. The sound through the headphone-out became slightly more neutral, and the level of detail improved but not to the same extent as through the line-out.
 
The Headphone Amp
I do not have much experience with headphones, and my purchase of the K701s was a bit poorly researched, I just read some very positive reviews and comparisons but I failed to realize that it needs a good amp to sound as it should. Now I've never heard the from anything other than my amplifiers head-out and through the STX, and in that comparison the sound-card wins hands down. From what I've read about the K701 my impressions with the STX as source echoes what most people say: big soundstage, crystal clear highs, great midrange and weak bass on some types of music, especially rock/pop. The volume level is no problem achieving, with Replay-Gain on in Foobar, regular listening volume is at 60% on the low gain setting. 
I've tried some of my other headphones through the head-out on the front of my computer, and it is very difficult to use IEMs such as my JVC-FX500 as the volume has to be set to 2-4% and at that level the cable leading from the soundcard to the front picks up some interference from hard drives and fans. Amping my vintage 600 ohm AKG K140 is no problem at all, the soundcard drives them loud and clear on medium gain.
 
Conclusion
This is a very good DAC and a pretty good entry-level headphone amplifier that costs as much as either would if they were external. The fact that it is from a big company such as ASUS means that the cost is cut by their ability to buy in bulk.
I can certainly recommend this card as a great entry to the world of hi-fi if you are using the line out from your stationary computer or when building a new one. The possibility to tinker with Op-Amps should also interest those who can't leave well enough alone...

The RS120 is a wireless headphone that receives an analogue radio signal, as such it is prone to interference from cellphones and is easily shadowed by having a TV or other shielding things in the signal path. This said, when they are getting a clear signal and the source is line-level and not amplified as from on-board sound from computers, they have no hiss while playing music and reaches ~50 m from the base-station without much distortion.
 
The sound is very pleasant, it is slightly rolled of at both extremes of the sound spectrum and there is a slight mid-bass bump giving the phones a warm tint. The level of detail is what you could expect from phones like these, good but not great. Positioning is okay, the drivers are angled witch gives a certain depth-perception but it is still a small sound-stage. These headphones are very forgiving of recordings and i sometimes prefer them over my k701s.
 
These headphones are great for watching TV and listening to music while doing the dishes or sitting outside in the garden. They are a supra-aural design that is extremely comfortable but they have very little pressure on the ears, this means that they are prone to fall off your head when leaning forward.
 
All in all these headphones are great for the price and do exactly what they are meant to do. I have owned these for 3 years and they have withstood being dropped numerous times without breaking so the build-quality is great.