I just built an AMD Athlon 64 3200 and I have the retail heatsink and fan. I also have one side fan and I get temps of:
No Load
CPU: 38
SYSTEM: 40
VPU: 36
Under Load (Unreal 2k4)
CPU: 49
SYSTEM: 47
VPU: 43
I also have the Cool and Quite enabled on my MSI K8T NEO.
My roommate has the Shuttle XPC barebose with an athlon 64 3000, and his runs at about 55 under full load and about 50 under no load. With those the heat has to flow through the heat pipe to the fins near the outside of the case. It's prettty cool.