Need USB conversion for DAC

I want o use a Spitfire DAC but how do I convert my USB signal first?
I also had a few higher end DACs in mind.
Check the HagUSB or Empirical Audio Offramp for conversion from USB to SPDIF.

Check the archives here and on Computer Asylum for more info.
DIY Paradise dot com has a cheap/easy kit, a complete USB DAC and you cannot go wrong with the Benchmark USB Dac IMHO.
Benchmark is a good DAC but I believe April Music DA100 with USB input at $695 is better to my ears.
Also the Trends Audio UD-10 USB Audio Converter