What it says above, here's what I've got:

AMD 5000+ X2 @2.6Ghz
1.5 Gigs DDR2 PC 5300/5400
Abit Kn9 Motherboard (Not the best motherboard in the world, onboard sound is shite)
EVGA 8800 GTS 320mb (Crysis = DIE, every other game is fine)
2 x 80GB PATA HD
1 x 160GB SATAII HD
700W PSU
Antec Lanboy 2 shiny shiny case
Logitech Wireless keyboard and mouse (Awesome)
19" widescreen TFT
500 GB Porn storage external
Creative 2.1 System (quite good I like this one)

And my question to you is what would you upgrade? I'm fairly certain I can't clock anything because of my motherboard which is the arse end of motherboards. I'd quite like to RAID my system but I'm unsure how and if I could...

I would upgrade to a SLI mobo and then get another 8800 GTS when you can afford it. Also make sure the mother board has dual-channel DDR2 slots and supports up to DDR2 800, and you can get a pair of DDR2 800's later (2x1gb), and use your ddr2 667 until then. RAID isnt something to take lightly, it's more for servers and mainframes that need the speed and redundancy it provides.