Second Hand CPU Advice for Encoding

[Snotuk]

I have an old PC that I want to use to do some HD video encode (x264 codec) at the minute it's got an Intel E6600 Duo Core 2.4 OC to 3.2 CPU, it's taking ruffly 24/48 hrs per encode running at 1 to 1.25 FPS
I'm not gonna spend a lot of money on a new chip I'm gonna go down the second hand route, so what I'd like to know what the best chip I can get to fit the listed below motherboard.

Thanks for any advice.

ASUS P5N-E SLI

CPU
Intel Socket 775 Core™2 Quad/Pentium® Extreme/Pentium® D/Pentium® 4/Celeron Processors
Compatible with Intel® 05B/05A/06 processors
Support Intel® 45nm CPU
Intel® Hyper-Threading Technology ready
BIOS needs updating to support Intel 45nm CPU

 

[Snotuk]

Thank for all your advice but was wondering any thing faster than the Q6600 that this MB can run.Not bothered about OCing will just run at stock speeds.

 

[Snotuk]

Thanks cmndr_andi & every one else I'll try & track down a QX6850,
And if not I'll go for the Q6700.

Thanks for all help