the s963 (3 heat pipes instead of the s964's 4 pipes) generally receives better temps b/c of the way the pipes are aligned on the 964, there is no pipe directly over the cpu die.
i had the same problem with space, i got the s963. my phenom idles high (37-40) but under prime95 and linx load only gets to 51 tops at 3.5ghz stock vcore (i'm still testing my temps to see how far i get). i got best temps using the thermal paste spread method
Thanks for the suggestions guys