I'm trying to figure out what's the best amp/DAC combo I can buy for $100-$150 for my needs. I currently have a Fiio E9 for my desktop where I do all my production, but I'd like something portable to use with my ultrabook on the go from time to time. Here are my needs:
 
1. It has to drive my 250 ohm DT880s
2. It needs to have a quality DAC. Ultrabook's sound card is garbage.
3. Portability (lightweight, small, USB powered)
 
My initial research leads me to either the Fiio E07k or the E17, since they are portable, and can also interface with my existing E9 if ever needed. They're also in my price range. I am a bit worried about their ability to drive my phones. Suggestions?

The E17 seems like a no brainier to me, especially if you already own the E9. Always been pleased with how it drives my headphones, although I don't own the 880's. E17 also has a eq which is a very underrated feature imo...

I ended up going with the E07k due to the price difference and that I don't need the optical port. Seems to have similar features to the E17 otherwise and drives my 880s well. Not really using it docked to my E9 though. I tested it and it works, but I have it hooked in through my sound card so the DAC isn't really necessary.