Now come on, one could think reading you, macenforcer, that a single quad would be so crippled to be useless... So a previous generation 2,66 quad mac pro is just so slow to be useless as well...
I can certainly understand the OP, I did choose the 8-core myself, but will I ever need the 8-core for my needs ? a 4-core would most certainly have been quite powerful enough for a very long time to come.
As a matter of fact, the 2,16Ghz core 2 duo iMac this mac pro is replacing was powerful enough for my needs, but I needed to have more than 3Gb ram on it, so it left the mac pro as the only choice (or go the windows way, which would have been much cheaper, but I would have hated it...)
Now, for the OP, and for everyone having spare cpu cycles, there is a reason to buy the 8-core and feel well about it ! Put the unneeded 4 cores to some use with BOINC...
phjo