Like PMK, I'm also using the Channel Islands Audio VHP-1 to drive the AKG K-701's. I've also added the optional VAC-1 power supply, and I've also upgraded the 'umbilical' AC cable between these units to the Revelation Audio Labs 'Parable' Cryo-Silver AC. I'm also feeding the VHP-1 and VAC-1 with Cardas Golden Reference ICs and AC. My entire headphone system has approximately 350 hours usage on it thus far, and I find it to sound very clean and open. Bass is a little lean, but it appears to be improving as further break-in occurs. Other threads on the K701's appear to mirror these observations, as several members indicate that these cans need 500+ hours to fully blossom.
But even at this stage, it's hard to fault the performance of the CI Audio combo at its price point. I feel it offers a tonally neutral and detailed presentation, very nice soundstaging, clear and articulate midrange, and very extended yet smooth highs.
Another key element in evaluating any headphone system is, of course, the quality of the music source. Feed this combo a good source, I feel you will end up with a very pleasing result.
[size=xx-small]Headphones: AKG K-701
Headphone Amp: Channel Islands Audio VHP-1 / VAC-1 combo + Revelation Audio Labs Parable Cyro-Silver AC umbilical
Source: Aurum Acoustics Integris CDP
Cables: Cardas Golden Reference ICs + AC power [/size]