Update:
Got my 2010 Mac Mini yesterday (very nice built, I must say). Thanks to some very generous advices from people reading this thread, I did some OS X tweaks and installed the latest Pure Music version (set for purity, which means no DSP effects and no volume control enabled + device exclusive access, Hog mode, etc.).
I have 8GB mem on order and other tweaks to do but, so far, with my system and to my ears, my Toshiba Core i3/HM55/4GB + 1GB dedicated for ATI video laptop, with Win7 64bit + JRiver and ASIO4ALL is far superior to the Mac Mini with PM v1.74, sorry to say.
In both cases my highly hot-rodded M2tech hiFace was used (clocks and data path tweaks + ultra-low-noise MOSFET linear power). Please dont get me wrong; the Mac sounds good, but it fatigues me over short period of time in comparison.
Of course, this is preliminary, so there is still hope, and still more to come, so stay tuned!
I will be also loading Win 7 (64bit) to the Mac Mini using bootcamp, so we can compare apples to apples. I am also thinking about borrowing some local San Francisco Bay Area Audiophile golden ears for a blind A-B testing. Volunteers are greatly appreciated, as always!
BTW, if someone here has experience with a better/purer sounding playback soft than PM, Id be more than happy to try it too.
Best,
Alex Peychev