My favourite DAP is the AK SR15 personally - extremely neutral (maybe slightly mid-centric), very small (easily fits in my pocket along with my phone or wallet) and pretty decent battery life too. Quite lightweight as well and extremely durable. The pairing with the Katana is goddamn exceptional, I'm listening to the two as we speak and I am melting...
Speaking of which I'd love to write another 3 paragraphs praising the Katana once again but i must hold back as I've done this numerous times on this thread
I have to say, I wasn't planning on an A&K as the price is usually above my pay grade. I was very fortunate to find a like-new SR15 here on head-fi for $450 shipped. I was very lucky and I agree it is a lovely player all around.