I decided I am going to buy the AKG K702 shortly (probably cyber monday) however, from what I have read, the K702's require A LOT of power in order to do the headphones justice. I am looking for usb dac/amp. In order to serve the headphones justice what kinda usb dac/amp should I get? Note: Im not exactly sure HOW much power is needed. I know that e7/e9 combo is a popular combo for many headphones but would there be a better alternative choice? I also don't wanna spend the 400$ on the nuforce icon HDP.