Update my CPU or video card?

[mylittlepony]

E6750- not overclocked per se, but using EIST to go up to 3.2 Ghz
Stock CPU cooling
Gigabyte GA-p35-ds3r
eVGA 8800 GTS 320 MB
4 GB Corsair CM2x1024-6400C4 (runnning at 400Mhz, 4,4,4,12)
Windows Vista 64 Home Premium

I was thinking about upgrading a component, but only want to do so if it's going to give me a significant boost.

I use this machine for gaming (Crysis, S.T.A.L.K.E.R., FarCry mostly), some video editing, and application development.

So, my choices:
Intel Core2 Quad Q9400 2.66GHz
or
Intel Core 2 Quad Q9550 2.83GHz (is it worth the extra $50 over Q9400?)
or
EVGA 896-P3-1264-AR GeForce GTX 260 SSC Edition 896 MB

(I'd consider other video cards too at the ~300 pricepoint).

Which would be a better bang-for-the-buck update?

 

[BTRY B 529th FA BN]

The vid card for sure.

 

[Roguestar]

Gaming upgrade hierarchy
GPU > CPU > RAM

Quad core will not benefit you in games.

Get something like the Radeon HD4870.

Also, you say your CPU is not "overclocked per se" but that it runs at 3.2GHz? How is this, pray tell? EIST allows a processor to run at lower speeds to save power, not clock up to higher speeds otherwise Intel would shoot themselves in the foot when selling higher-rated processors.

 

[Sunrise089]

4870

 

[MarcVenice]

gtx260 or hd4870 ... No question abt it. The gts 320mb really gets bogged down in Clear Sky ...