Mac vs. PC differences to Airport Express?

Thanks for all of your responses so far.

Audoiengr: Thanks Steve, for answering my first question. It's good to know that iTunes Windows XP to Airport Express is the same quality (however low) as Mac iTunes to Airport Express.

The Pace-Car at $1400 is pretty steep for me at this time. If I were to eventually invest that much, how would that compare with getting my Benchmark modded to accept USB?

Right now I'm interested in a $200 upgrade. I could get a Trends Audio or equivalent USB/digital converter and go
PC > Converter > Benchmark

Marco and Jax2: I know the Mac platform is solid for USB out. I have an old Mac iBook I could use for that config, or I could buy Windows Vista and stick with my PC. I want to stick with iTunes. I've read that Foobar and ASIO are too much of a headache. Would iTunes for PC w/ Vista equal iTunes on a Mac for USB out?

And would a $200 USB/Toslink converter be better than sticking with wireless to Airport Express. Either one would end up in my unmodded Benchmark DAC-1

Can the Mac Mini be used instead of an Airport express for wireless use? If so, is there any advantage to sound quality over an iBook wireless to AE?

Steve,
Which would give me better sound:

PC>Airport Express>Pace-Car>unmodded Benchmark DAC-1

or

PC>USB>supermodded Benchmark DAC-1(w/ additional mod to add USB)?

Anybody:
Since either of the above would be done 'down the road', what would be better for now:

PC > $150 USB/Toslink Converter > Benchmark

or

PC > Airport Express > Benchmark?

Any Recommendations for a $100-$200 USB/Toslink Converter?

Thanks for all of your advice, guys. I have decided to get a Trends UD-10.1 USB converter for now. I will use my iBook laptop attached to an external hard drive. I will go

Mac iBook >Trends USB converter > S/PDIF cable > Benchmark DAC-1 > analog out > Musical Fidelity A5 Integrated > speakers.

Down the road I will either mod my existing Benchmark DAC or upgrade to a USB DAC, but for now this looks like the best way to improve my sound greatly for just $150.

The only question I still have is what cable format to from USB converter to Benchmark DAC. I can use my existing Stereovox HDXV S/PDIF to BNC cable
or
I could use an XLR cable between the two.
Any feedback on that?

Thanks, Mark. I already own the coax cable, so I'll try that first.

Steve, would you keep the Benchmark's volume in 'calibrated' or 'variable' mode?

Would replacing the stock fuses make a difference?