wrong - LFS is usually CPU limited due to physics calculations!
And btw, 2.5 is a bit woosie, drop the multi, raise the FSB, raise the vCore, pray the temps dont raise much!
summer is on its way as well and I'm only using air cooling so 2.5 is plenty, it idles most of the time anyway and only gets a bit of a workout during LFS or when rendering in 3dsmax. Currently idling at core1-38oC core2-30oC Vcore 1.45 from 1.35.