Need help with Dedicated music server.

I am really confused with a selection of a dedicated music Server and need some info. I currently use a Toshiba laptop/J River Mediacenter/Benchmark USB DAC. I have ordered a Berkeley Designs Alpha DAC. As you may well know the Berkeley does not support USB at this time. I need a Music Server Solution to The Berkeley Alpha DAC. I have heard that many users prefer the Mac Pro/Almarra server. But with the release of Windows 7/ Wasapi J River Server. Also your hear good things about XXHighend. Please can someone give some Impressions of each of these Music servers?

Thanks in Advance,

Johnny