I beg to differ, I struggle to fully utilize even 4 cores on my dual X5690 rig. My 15 minute system load average is never usually higher then 1.5, this means I only have enough work to keep 1.5 cores fully queued with tasks. The other 10.5 cores are simply burning electricity.
In my opinion, if you are on a budget then the best processor option is the X5677. You would be better off to invest the money you saved into a PCIe SSD.
How often are you Zipping/Unzipping that you need to spend an extra $280 on X5690s? Like I originally said, unless you know you need 12-cores (i.g. video production) you'll be perfectly content with 8 x 3.46 GHz cores.