Um, wow. Had a dual 2.4ghz 8 core 5,1 and wanted an upgrade. Picked up on ebay 2 x 2.93ghz Nehalem quad core cpus for $125 each. Dropped them in just now and increased my geekbench 32bit score from 13000 to 16279. That has got to be the best dang upgrade for the money I have ever seen. I know I went from a 32nm cpu to a 45nm but the temps are the same, fans are the same and watts only increased from 80 to 95 for each cpu. The increase of 3300 in geekbench is amazing. If you have a dual 4,1 or 5,1 and you don't have at least these cpus you are not having fun. Next step up is going 6 core but those puppies start at $500 each. Can't beat $125 each.