I've been away from Head-Fi for a long time, since they changed the theme actually. From what I remember, Little Dot, Schiit, Fiio (as mentioned), and Nuforce were very well-regarded. If you want to build something insane, I remember many people building the Gamma 2 which likely remains one of the highest-end DACs on the market. The Nuforce uDAC is a great choice though, it's relatively inexpensive, sounds great, and supports 96kHz/24bit over USB. They also make a small amp called the Icon which isn't as inexpensive, but would fit your needs. Reviews:
http://www.head-fi.org/products/nuforce-icon-hdp-high-end-headphone-amp-usb-dac-preamp
http://www.head-fi.org/products/nuforce-icon-udac-3-high-resolution-usb-digital-audio-converter-dac-silver
Another good choice for a small T-class amp: http://www.tnt-audio.com/ampli/trends_ta10_e.html
http://www.head-fi.org/products/nuforce-icon-hdp-high-end-headphone-amp-usb-dac-preamp
http://www.head-fi.org/products/nuforce-icon-udac-3-high-resolution-usb-digital-audio-converter-dac-silver
Another good choice for a small T-class amp: http://www.tnt-audio.com/ampli/trends_ta10_e.html