Arcam is coming up with a usb dac + headphone amplifier called rPAC
Pricing seems to be around 150 Pounds
It has a line out as well.
My next item on wishlist. (i hope it has the 6.3 mm socket)
Found the following links:
Arcam - rPAC - USB DAC / Headphone Amp
CES 2012: Arcam adds rPAC...