First of all, I'm sure someone with more knowledge will let you know how these systems sound. I'm just going to say a few things that may or may not help you.
I too am doing research for an AMP for my HD600.
From what I've gathered, If you are want the "tube" sound, are okay (or even excited) by the idea of rolling tubes, and know that tubes have to be replaced after a certain amount of time (Depends on tube, normally 5,000-10,000 hours), then go for Tube Amps like MK IV / MK IV SE / Valhalla / Lyr / WooAudio 3 etc.
First step for you should be choosing your "path". Decide between Solid-State and Tube.
From there, just look at the SS or tube amps, and it will make your life much easier.
Just so you know, I have HD600 and Audioengine 2.
Note: Following prices don't include shipping, and you might be able to find them cheaper. I'm listing them so that you have a good idea about what AMPs you shouldn't look at (because of budgetary reasons).
While doing your research, have a look out for units that don't have the RCA outs for your Audioengine A2s (For me it's not that big a deal as I can feed my A2s with Essence ST).
If you want DAC/AMP combos (Solid-State);
- DACmini CX or PX (has preamp) - $800 and $1500.
- Yulong D100 - $400 (On sale on Ebay $100 off - Sale ends in about 3 hours).
- Asus Essence One - $400-$500 (Not many reviews out yet).
- Burson HA-160DS - $1200.
- Audio-gd NFB-12 - $200
- Audio-gd NFB-5 - $330
- Benchmark DAC1 - $990 (many options, which increase price).
- Nuforce Icon HDP - $449.
If you just want a separate AMP (Solid-State);
- Schiit Asgard - $249.
- Matrix M-Stage - $280.
- Little Dot MK V - $279.
- Burson HA-160 - $650.
- Meier Audio 2Stepdance - $399.
If you want a dedicated DAC (Some are DAC/AMP combos);
- Schiit Bifrost DAC - $349 or $449 with USB input.
- Burson DA-160 DAC - $950.
- Cambridge Audio DacMagic DAC - $429.
- Matrix Cube DAC/AMP - $300
- Audio-gd NFB-3.1 or 2 DAC - $299 and $450
- Other Cheap DAC options: Fiio D3 / D5 / E10 ($30-80).
- If you don't want many input options (versatility) and are only going to use USB, only then: HRT music streamer 2+ DAC $150, DACport DAC/AMP $399
Or use any of the above DAC/AMP combos as a DAC and attach your choice of a dedicated AMP to it.
If you want a Tube AMP;
- Schiit Valhalla - $349 (you can't roll tubes with Valhalla) - Said to match very well with HD600/650.
- Schiit Lyr - $449 (Only Lyr has additional outputs for your Audioengine A2s)
- WooAudio 3 - $495.
- Little Dot MK IV / SE - $289 and $389
Now, I'm a little tired :)
Mix and Match, narrow it down.. and I'm sure while doing that you'll read many opinions on lots of combos.
After your research, do post where you narrowed it down and any questions you might have...
Hope this helps!
Edited by Jogiya - 11/29/11 at 6:46am