i really can't recomend the 1U version if you don't have a separate machine room .. it is definately too loud (the fans with little diameter are very noisy) ... in fact i cannot recommend any server system in a studio except if it is in a really first class sound-absorbing case.
actually the components (harddisks, CPU cooler, HD cooler) are a little bit noisy.
the supermicro systems go up to 64 GB, the 7-series up to 192 GB RAM, but the decision for this system was too complex to answer with a simple *why this processor*.
if you don't need it for certain multiple purposes have a look at intel S5000 series motherboards and 3U housings.
on a predecessor of herb's system (netburst architecture) i had 48 instances running with about 10% CPU - so such practical experience has also impacted selection of the model.
christian
and remember: only a CRAY can run an endless loop in just three seconds.