http://www.head-fi.org/forum/thread/508076/review-leckerton-audio-uha-6s-portable-amp-dac
 
That's a link to my full review. In summary:
 
the Leckerton UHA-6S is one of the best portables amps I've used (and I've used a lot). It has a very high end sound, both as an amp and a DAC. The battery life is very good, it charges via a simple USB cable, it works with almost any headphone thanks to dual gain settings, and it even has socketed opamps inside for people who are inclined to tweak. It is built by a small audio company in the USA who offers excellent support, a 30 day money back guarantee, and a full 2 year warranty. There's really not much more one could ask for in a portable amp. You can save $20 by getting a USB only version if you don't think you will ever use the toslink input, but I think it is a nice option to have. I don't understand why this amp isn't more popular.

http://www.head-fi.org/forum/thread/513019/review-maverick-audio-tubemagic-a1-integrated-amp-pre-amp-headphone-amp
 
That's my detailed review. In summary:
 
The Maverick A1 is an excellent tube headphone amp for the price, period. The fact that it is also a good tube pre-amp and hybrid amp for full sized speakers is just a bonus. The sound is ultra smooth and warm, with a great low end.
 
The amp section is powerful enough to work with lots of speakers provided they are reasonably efficient. You get surprising volume in small to medium sized rooms, with the same characteristic excellent bass response, smooth rich mids, and gently rolled off highs.
 
The one minor downside is with the build quality of the case: once you take the cover off, it is tricky to get the screw holes lines up again. Additionally, my unit had a bit of a "wobble" caused by unevenly spaced rubber feet on the bottom. That was easy enough to fix but did act as a reminder of the low price.

http://www.head-fi.org/forum/thread/515068/review-hot-audio-dac-extasy-usb-dac
 
That's a link to my full review.
 
In summary, the Hot Audio DAC Extasy is a hand-built USB only DAC with a great warm sound. It uses a Wolfson WM8501 DAC chip which has a somewhat unique feature: direct line driver capability. This simplifies the design because the output comes directly off the DAC chip itself, with no post processing required. It also allows for a direct headphone connection; it isn't a traditional headphone amp, but works quite well.
 
The DAC Extasy is a strong offering but it plays in a price class with many other great products, and it seems like for each extra $20 you spend you can move up the ladder a bit. Still, if all you need is USB input and like a warm sound, the DAC Extasy is hard to beat.

http://www.head-fi.org/forum/thread/516993/review-matrix-cube-dac
 
That's a link to my extensive review.
 
In summary, the Matrix Cube is a cross between the Cambridge DacMagic and the Musical Fidelity V-DAC. It matches the detail of the DacMagic with the smoothness and musicality of the V-DAC, all for a lower price. And don't forget the built in headphone amp, which is very much on par with the Musical Fidelity V-CAN/V-PSU combo. In my humble opinion this is a best buy right now in the $300 range, and would make a very solid foundation for someone building a system.

http://www.head-fi.org/forum/thread/475618/matrix-m-stage-amp-review-simple-cheap-and-excellent
 
That's a link to my full review, which has become a very long thread.
 
In summary:
The M-Stage is a clone of the Lehmann Audio Black Cube Linear, which is a high end headphone amp selling for around $1k. The M-Stage matches or exceeds the real thing in every aspect. It features a socketed opamp in the output stage so you can upgrade or try different things yourself (the Lehmann does not allow this). It is built like a tank, perhaps not the most pretty thing in your audio setup but it does have a certain utilitarian charm. At this moment I think this is one of the best choices out there for people to experience high end sound at a reasonable price.

http://www.head-fi.org/forum/thread/510802/review-unique-melody-aero-custom-triple-driver-iem
 
That's a link to my extensive review. In summary:
 
The Aero has the Unique Melody house sound, which will appeal to some but not all. Lovers of AKG K701, Etymotic ER4S, Sennheiser HD800, AKG K1000, or Electrostatic headphones in general will likely find these to be almost perfect. Fans of Denon D2000/5000/7000, Beyerdynamic DT-770/DT-990, Sennheiser HD650/IE8, or other bass oriented headphones should probably look elsewhere. For the price, they are extremely competitive if you like this sort of sound signature.