As I was saying a few pages back. I recently swapped out the 25mm Scythe fan (it came with my old Scythe cooler) I had been using as the push fan in my push/pull configuration along with the stock h50 fan. I swapped it for an UltraKaze3k and I think I may have only gotten 1C difference. I also relapped my CPU and this time I used IC Diamond TIM. I went through a lot to test this out and got nothing in return... boohoo.
Corsair fan + Scythe 25mm:
Corsair fan + Scythe UltraKaze3k 38mm
Freshly lapped (re-lapped) Q9550:
How I mounted the radiator and fans:
I guess I'll be switching back soon because the UK3K isn't worth using for 1C improvement. I think I was hitting 60-61C under load which isn't bad but I thought I'd see a difference using such a powerful fan. While people think this thing is loud (and it is) it moves way more air than the fan it replaced. Both push fans have a 25mm "shroud" (empty fan).