What upgrades should I make for Warhammer Online?

My computer runs Warhammer Online fine in areas with 40 or less Players. I get the bad "lag" and FPS when it is 41+. I would just like to know if there is a way to upgrade anything in my rig right now, with maybe being able to keep my VGC (ATI Sapphire HD3850) Or if I need to replace it also... My biggest question is, where would I see the biggest improvement on my rig, if you could only improve one spot. Thanks for your time!

Specs:

Windows XP (SP2)
Processor: Intel(R) Pentium(R) 4 Prescott CPU 3.00GHz (2 CPUs)
Memory: pqi POWER Series 1GB (2 x 512MB) 184-Pin DDR SDRAM DDR 333 (PC 2700) (2048MB RAM Total)
GFX Card: ATI Radeon HD 3850 512MB 256-bit GDDR3 AGP 4X/8X HDCP Ready
Mobo: Asus P4SD-VX


Again, thanks for your time. I run WAR at around 22 FPS at all low settings. I just wanna have some more "umph" to the platform and try to get another year out of her until she just can't go on!

Thanks!

Are there AGP versions of the HD4xxx series available??

or he could try and get a P4 965 EE for $200 and get a nice compact water cooling system for $100, maybe up the ram to 4x1GB ddr-3200 for $100 too.

Thanks for all your replies. I appreciate your time and input. I think I might just keep what i have and do with it till I just make a new one!

Thanks again!