its not really what you're looking for so perhaps put it in the 'honorable mentions' category, but I love my little Fiio K3.
This is a review and detailed measurements of Fiio K3 DAC and portable headphone amplifier. I got talked into buying it earlier this month due to popular demand. Fo you all's sake, it better measure well! :D The Fiio K3 is quite cheap for such a combo product and costs just USD $109...
www.audiosciencereview.com
It doesn't have enough power for most audiophile headphones but I use it for IEMs and have never heard the noise floor, so the lackluster SINAD doesn't bother me. So what does sell this device for IEMs? its tiny, I have it command stripped under the front edge of my desk, perfect placement, it has a superb volume control, it also has a 2.5mm balanced out as well as the 3.5mm, and it can act as a digital bridge with toslink and coax outs, both of which work simultaneously, so you can daisy chain other devices like a BT transmitter or another DAC.
Its USB powered which is a double edge sword, its convenient where it works well but you need a USB port with enough power (USB 3 perhaps) plus it needs to be pretty clean, the K3 doesn't do a good job of filtering any noise coming through the shielding, though that has only caused me a problem with a 2 pin laptop.