Best amp for AKG K701 used/new?

These headphones reveal from the music sources something I haven't heard before, but with the right amp I can realy get more dynamics and bass...
Now I listen them through the recording interface of Alesis ML digital recorder wich has quite powerful headphone output but still still not eough for AKGs. Some of the recordings with high level are OK to listen around 1 o'clock but some wouldn't go OK even at its maximum.
Obviously it's not enough and I need something more powerful. I also prefer to have balanced inputs and balanced output bypass so that the device could be placed in the tape loop with the recorder.
Knowing lots of headphone amp brands, I would figure that not all of them will even have enough power even compared to my Alesis output so I don't want to make mistake selecting the same what I already have.
Help me with the choice within $500 used or new.
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I have enjoyed listening to my AKG K701 headphones using a Consonance Cyber 20 headphone amp. I also auditioned the RSA Raptor which was a nice combo as well. The RSA Raptor is out of your price range ($1175); however, you may want to look into the RSA Emmiline HR-2 and XP-7. I'm not sure if Consonance has a US distributor at this time. You may want to post this question on Head-Fi.
Check out Woo Audio WA 3+ model.Tube based headphone amp for low impedance headphones,unbalanced input only.They are located in Queens,NYC.
I found the one that matches my needs, but still would like to hear feedback which I couldn't find. It's
ATI HD100.
This company exists from early 90's and has pretty large pro and home audio/theater equipment selection.
Luxman line of current integrated amps.
I finally spotted a good deal on Consonance M20 amp. The only downside that it doesn't have neither extra set of inputs nor bypass output to have it in the chain with mentioned above Alesis recorder. Either I will do the mod myself (done that in the past with different equipment) or I should find the reputable service to do so.