Were you using iTunes to rip and playback? There really
should be no issue whatsoever, in theory, with the new Minis.
Personally, I have a 2010 2.4 GHz C2D with only 4gig RAM
with 10.8.2 and my ALAC files play back flawlessly. So, a new
Mini with 4gig should not be problematic. They were however ripped
quite a while back with much older versions of iTunes. So, a new
Mini with 4gig should not be problematic from a hardware standpoint.
Also, I have done 24bit,96kHz rips of LPs and saved in ALAC
and they also have no playback issues.
With all the issues with the latest iTunes, I would think that
ripping/playback with iTunes would be more at fault than the hardware,
although I have not seen any playback issues myself.
I would suggest perhaps trying playback/ripping on something
other than iTunes before blaming the hardware at this point.