Alright Geeza's, Nubs Needing Pro Advice?

Alright fella's, im new to the whole PC mod scene but ive always played games now ive landed a top job i feel its time to have a sick rig.

I found out about 3dmark05 browsing the alienware website and i decided to run a test to see how i compared. I scored 2206 on the demo version (excuse any nub language ) heres my current rig:

Advent Rig:
Windows Xp home
3.2ghz p4 800mhz fsb HT prescott CPU.
2 x 512 PC2700 (DDR333) Ram.
1 x 200 gig HDD (not sure what type to tell the truth )
PNY Geforce 6600 256. AP x8

Basically, is it to my understanding AGP 8x is old hat now and is my score average for this rig? do i either OC the cpu, 4 gig of corsair ram / best agp 8x gfx card to date, mod the bios and get win xp pro and a modders case? or shall i get an enitrely new rig, pci-e / sli enabeld? i was thinking alienware or dell xps? Baring in mind i would like to spend a MAX of £2,000 Preferably £1500

I do alot of DJ work / Digital DJ work and love my games, im asking you pro's for some advice as to what i should do. Im a complete nubstastic on the matter this current machine works fine but i'd like it to either be the dogs bollocks or get a new top rig?

Thanks, apreciate it

Sir0x0r