I have the SX38P2 Pro myself and I run 4gb DDR with the Q6600 Quad cpu and a dual slot 8800GTS G92 core fx card and I will say that heat is a major issue in the SX38. With the stuffy weather atm the q6600 which is now at stock speeds to help cool it will sit around 56c and full load will hit 64c. No matter what I try won't help cool the system. I was even looking at a single slot fx card to replace the 8800GTS to keep the heat out the case.
I have replaced all the shuttle fans with higher spec ones to get more air out the case and that helped marginally (All because the shuttle fans died within 4 months and I wasn't RMA'ing it for a few fans)
If you have the money I would go for the SX48 or infact the newer SX58 and the DDR 3 route and get quite a few years out of it
Mind all reports I am seeing on the SX48 and SX58 the heat issue is still there if you are running gaming components. I love the SX38P2 but the sheer amount of heat in the system isn't good.