http://www.head-fi.org/t/662869/maverick-audio-tubemagic-d1-amp-dac
There's that, I'd think a nice tube amp would match the k701 well. I like tubes with my dt 880s very much!
or trying going with an Odac [with rca out[ and one of these
http://www.garage1217.com/graphic_design_007.htm
Porject Starlight, new from them for about 189, they are the same guys who make the Project Sunrise II which I've heard alot of good about. So if u able to wait, get a 100 dac and look for a 200 hybrid tube amp! I have a Millet Whiplash that I like very much!
I also have an Indeed G3, which cost me $100 that's,,, well a start hybrid tube with a BASS boost button. That might be the cheapest way to go. Still though, I would think a tube would match the k701s well, as my neutral and some times bright dt 880s like tubes