Which cpu for Tmpgenc ?

[hyperfighting]

Hello guys, advice needed. Ignore the rig in sig, have just built a new machine just for encoding with Tmpgenc, it has a q6600 @ 3.4Ghz (vid = 1.325), 4 gig ram on a p45 based motherboard. The cpu wont clock any further without putting too much vcore into it, we are talking like 1.55v+ for 3.6ghz (currently at 3.4Ghz 1.44v, ninja cooler). The question is, if I replace the q6600 with say one of the newer stepping E8xxx series dual cores and clock it to 4Ghz or a bit higher if possible. Will I see an improvement in encoding times even though there will be a loss of 2 cores but benefit of the 2 faster cores + improved penryn multimedia extensions which Tmpgenc can make use of ??

Thanks.