I dunno about th GW FOP 38.
However, just switched my Alpha 6035 for an Alpha PEP66 and (using arctic silver) lowered my core temps from an average of 109 to 114F to 102 to 107F.
BTW - I am running a duron 800 oc'd to 1 gig on an abit kt7-Raid MB. The fit of the pep 66 is tight - but very workable- just mount the shroud and fan to point the other way towards the fron of your case and you'll clear the capacitors (you gotta assempble the alpha's anyhow- very simple procedure).
Worth mentioning also is this - prior cpu temp ranges of 109-114F were with the sides off my old case ! With the side on the cpu temps averaged about 5 degreees F higher.
My new case is an antec 830 sx with four fans- sweet case !
The alpha pep66 is a little noisier- but overall, my system is quieter than before because the antec case ps is quieter than my old sparkle unit.
Good luck- hope to have helped .