where to start

The advantage of Mac is that programs like Amarra (certain revs) and Pure Music eliminate the SQ issues with iTunes.

PC has some programs that attempt to do the same thing like Jriver and Media Monkey with Kernel Streaming plug-ins or WASAPI, but typically do not do quite as good a job as the Mac programs. Jplay may be the exception.

Steve N.
Empirical Audio

Steve, you are certainly entitled to the opnion that say running JRiver in WASAPI mode is inferior to say Pure music on a Mac, but there is absolutely no broad consensus on this. For example, Alex Peychev is on the record saying he preferred his Toshiba laptop running JRiver over a Mac mini, and there are many others with similar preference. Strangely I have not come across any double blind A/B comparisons, which would be interesting. Also, very high grade asynchronous converters like your offramp in the chain, should further reduce any perceived or real difference in SQ. The Mac / PC usually boils down to operating system and server application preference on the basis of usability / stability / ease of setup. I do not think you can categorically ascribe superiority in SQ to one over the other.

03-18-12: Edorr
Steve, you are certainly entitled to the opnion that say running JRiver in WASAPI mode is inferior to say Pure music on a Mac,...

I couldn't agree more!