Upgrading Homebuilt...Advice Please

Hello

This is my set-up right now. I am looking to make an upgrade but I am not sure which area to attack. I was thinking of getting another 1gb 4870 and doing crossfire but maybe I should try a new processor or SS HD to improve performance..let me know what you would do if you were me..thanks

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: heavy gaming occasional school work

PARTS NOT REQUIRED:this is my set up to date:


OCZ Reaper HPC 2GB (2 x 1GB) 240-Pin DDR2 SDRAM DDR2 1150 (PC2 9200) (x2 4gb total)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


Rosewill Xtreme Series RX950-S-B 950W Continuous @40°C ,80 PLUS Certified, ATX12V v2.2 & EPS12V v2.91, SLI Ready CrossFire Ready, Active PFC "Compatible with Core i7, i5" Power Supply
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


ARCTIC COOLING Freezer 7 Pro Rev.2 92mm Fluid Dynamic CPU Cooler
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


ASUS P5Q Pro LGA 775 Intel P45 ATX Intel Motherboard
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


XCLIO A380BK Fully Black SECC 1.0mm thickness ATX Full Tower Computer Case
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


Western Digital Caviar Blue WD2500AAJS 250GB 7200 RPM SATA 3.0Gb/s 3.5" Internal Hard Drive -Bare Drive
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


Intel Core2 Quad Q9400 2.66GHz 6MB L2 Cache LGA 775 95W Quad-Core Processor
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


(I have a diamond but couldn't find it on newegg)
Radeon HD 4870 1GB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card
http://www.newegg.com/Product/Product.aspx?Item=N82E168...


LG W2286L Black 22" 2ms HDMI Widescreen LED backlight LCD Monitor 250 cd/m2 DC 2000000:1
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Standard keyboard, mouse and 2.1 speakers


PREFERRED WEBSITE(S) FOR PARTS: newegg.com

COUNTRY OF ORIGIN: USA

PARTS PREFERENCES: I prefer staying with Intel processors but go back and forth with ATI and Nvidia video cards, currently with ATI and loving it

OVERCLOCKING: No

CROSSFIRE: Maybe crossfire, benchmarks show a decent fps increase

MONITOR RESOLUTION:1680x1050

ADDITIONAL COMMENTS:I have $200-$300 to spend on this upgrade..any info is appreciated