Upgrade recommendations for existing system

Hello,
I have a system I built back in early 2007, that I recently upgraded to windows 7, and I'm looking for advice on how to improve my performance. I appreciate your feedback. It's been a while since I've looked at parts, so I'm not sure where to start, or what will work with my existing system listed below. Be it RAM, CPU, graphics card, MOBO, I appreciate your time to respond:

APPROXIMATE PURCHASE DATE: within a month

BUDGET RANGE: negotiable

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: heavy photoshop, web design, possible future windows media system.

PARTS NOT REQUIRED:
* 1 x COOLER MASTER Centurion RC-534-KKR5 Black Aluminum & Mesh bezel, SECC chassis ATX Mid Tower Computer Case 400W Power Supply - Retail

(replaced PSU above with this since order)
*1 x PC Power and Cooling S61EPS 610W Continuous @ 40°C EPS12V SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply compatible with core i7 - Retail

* 1 x GIGABYTE GA-965P-DS3 LGA 775 Intel P965 Express ATX Intel Motherboard - Retail

* 1 x BFG Tech BFGR76256GTOCE GeForce 7600GT 256MB 128-bit GDDR3 PCI Express x16 SLI Supported Video Card - Retail

* 1 x Intel Core 2 Duo E6400 Conroe 2.13GHz LGA 775 65W Dual-Core Processor Model BX80557E6400 - Retail

* 1 x OCZ Platinum 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400) Dual Channel Kit Desktop Memory Model OCZ2P8002GK - Retail

* 2 x Seagate Barracuda 7200.10 ST3320620AS 320GB 7200 RPM SATA 3.0Gb/s 3.5" Hard Drive (Perpendicular Recording Technology) -Bare Drive

* 1 x HP 18X DVD±R DVD Burner With LightScribe, 12X DVD-RAM Write Black IDE Model HP940I LightScribe Support - Retail


PREFERRED WEBSITE(S) FOR PARTS: newegg.com

COUNTRY OF ORIGIN: USA

PARTS PREFERENCES: indifferent

OVERCLOCKING: no

MONITOR RESOLUTION: 1680x1050

ADDITIONAL COMMENTS:

Your motherboard should support a quad core, so it could be worthwhile to spend a few bucks on a q9550 or q9650. Also maybe look into a couple gigs of RAM (if you installed 64 bit), as that will help you out a bit as well. Maybe even a 48xx series graphics card.

Just looked up my mobo, and it does support quad core the RAM it supports is:

1. Supports DDR2 800/667/533 memory
2. Dual Channel architecture support up to 8GB by 4 DIMM slots

will have to look into some options for that, since the RAM I originally purchased has been discontinued I guess.