Worth upgrading for my Q6600?

Which is the processor to get for someone who games at 1680x1050 on a 22" Samsung 226bw and also does video encoding in sony vegas. Rendering WMV to MPG or AVI for 20 minute video normally takes my system 15 minutes each video running with its current q6600 g0 processor. The speeds of this system are 100% stock.

I normally play shooters at 1680x1050 w/ all details on high and my AF at 16x + 8x CSAA for my GTX 260 896MB Superclocked.
There isn't a single game I have that I can't run. My main concern is on the time required to encode and just having a faster system in general.

Is it even worth upgrading my Q6600?
Should I upgrade from my current EVG-A 680i SLI A1?

All I do on this pc is render videos in sony vegas 9.0e pro, work in photoshop CS5, play my games, program in c++ with visual studio, and chat/surf the web.

I am on a budget of $300.00-$350.00 which includes a cpu+mb, so I am considering either AMD or Intel

Edit:
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I have water cooling currently, but I am ditching it all together. It worked great for awhile, but now it slows down and freezes up alot even after clearing and refilling the lines + the fan noise is too high. After I work on my pc for 4-6 hours it slows down almost to a crawl. I reboot, then everything is fine.

The OS is windows 7 home premium 64-bit.