it all depends on how sensitive your headphones are, there are some IEM's out there that can make even the blackest headphone amps display hiss, power conditioning helps greatly as well.
Yea pure speculation regarding the USB receiver, its a good guess though, the T1 uses a TE7022L, and the next logical evolution is a TE8802L.
The Yulong D200, the DA8's little brother looks promising, XMOS receiver, 32ohm:1W etc, its bound to be listed here...
