Upgrading from E6400 or new system?

I'm looking for a system that will keep up with my HD5770 in games. Would it be worthwhile to upgrade my CPU or just save and wait for post-Christmas deals?

I have a Asus P5N-E mobo with a C2D E6400, 4GB ddr2 800, 64GB ssd, win7-64.

It's getting old and I'm not having much luck mixing it with overclocking and games.
I'm looking at getting a Q9400 for $175 http://www.digiconcepts.com/intel_cpus_257.htm
Looking at the gaming hierarchy chart that is 5 steps up. Or is another CPU a better fit?

From what I read people say the Q9400 works despite it not being officially supported.

Thanks for any advice.