is it worth upgrading?

[beer_puppy]

I was thinking of upgrading my gaming system, but would i notice the difference if i did? I have a MAX of £500, then in about 9 months i can spend another £500.
I have..

Athlon FX 55
Asus A8N-SLI Deluxe
Corsair 1GB DDR XMS3200C2PT TwinX
XFX GF 6800 ultra
2x 74GB WD Raptors
Thermaltake 680W PurePower PSU
CoolerMaster Stacker 810

Option 1 - Change CPU, MoBo, RAM + keep everything else
Option 2 - Change GC
What would you do?

 

[beer_puppy]

I mainly play cs:s, bf2, and some rts,
I have a 19" Hyundai ImageQuest Q995, so it can handle upto 1600x1200

 

[beer_puppy]

ok, cheers for the help