I was in a similar spot, looking for a headphone amp with some EQ capabilities (mainly bass altering) to use with a Rocoo P I just purchased. After some research I was going to buy a Headstage Arrow but the $300 price and wait time left me looking for a quicker/cheaper alternative. After all, my hearing may not detect much, if any difference, with an amp so I decided to get a Fiio product because of the price to performance ratio everyone seems to rave about. The E17 came back in stock at Micca store and I almost ordered that but stumbled on what appears to be a Pyle version of the E7 (http://www.amazon.com/GSI-E7-AB-Portable-Headphone-Amplifier/dp/B00654LOCS) which just dropped to $54.99 a few days ago. Reviews are mixed, main problem seems to be some issues with the display not working, but Amazon has always been good to me so I'm sure if there are any issues they will be resolved quickly with no hassle.
Worst case, if I notice no audible improvement connected to my Rocoo P I'm only out $55 and I still have a device I can use with my laptops/desktops.