PC for Antelope Zodiac / Perfectwave DAC Shootout?

I am using a perfectwave DAC + bridge + modwright 36.5 LS/PS preamp to stream flacs over my network. Very happy with the sound, but intrigued by the idea of getting better SQ for less $$$ I will soon be auditioning an Antelope Zodiac Gold + Volticus over USB, directly into my poweramp. Being able to take out the modwright alone would pay for the new DAC. My only concern is the PC I will be using for this shootout. I have a Dell laptop and an Asus media PC, both with USB 1.0.

If I opt for the Zodiac I will go all out on computer source (may be mach2music), but I don't want to invest before knowing if I even want to go down the USB path.

In you estimation, is there any chance of the PC used in my shootout distorting the outcome? Would I be better off using my Marantz ud9004 S/PDIF source for the Zodiac, and then get a better computer if the Zodiac wins the contest?

Or are the difference between computer sources small and will I be able to conclude which is the better DAC using a mediocre PC as the source for the Zodiac. Any advise on how to set up the hardware for the shootout is welcome.
I run a Zodiac Gold + Voltikus off a mach2music server running puremusic. Beware that the Zodiac needs at least 300(!!) hours of break-in before getting to its reference quality sound. It'll be miserably coarse and constricted straight out of the box but boy is it great once it settles in! As to support, the usb2.0 implementation is one of the attractions of the Zodiac Gold: I am using the spdif on a wadia 170i with Neutron clock conversion but the Mac is far superior
I bought a Mac Mini 2009 (with SSD and 8GB RAM) for the shootout. If I keep the Zodiac and stick with USB, I may look into the 2011 Mach2Music..