From what I see, you have a 7600Gt, and are happy, so games aren't your priority. So what is? What OS are you using?
If it is 32Bit then you are capped at 2Gb (3Gb if you are happy with it running a bit slower)
http://www.overclockers.co.uk/showpr...d=8&subcat=813
I would go for the cheapest board that serves the purpose and spend the rest on a CPU.
http://www.overclockers.co.uk/showpr...d=5&subcat=807
These are just suggestion btw. That leaves £142 (-P&P if you are inc in your £200) for a CPU
http://www.overclockers.co.uk/showpr...=6&subcat=1328
Those are getting great reviews, the board is AM2+ but it may need a BIOS flash, and you will have to check to see if can run them.
http://www.overclockers.co.uk/showpr...=6&subcat=1033
Again, BIOS flash maybe and compatibility, just check beforehand.
If you grab the X4 Phenom, you are £20 clear on your budget, so that is something you could spend on a better Motherboard.
Don't forget, if you get an AM2 board you are stuck with AM2, AM2+ will support Phenom2 CPU, so that future proofs you a bit, so maybe, a cheap AM2 CPU in a more expensive AM2+ board might be a better choice. It depends on what you want it for.
Or......
Stick with that OCZ RAM
http://www.overclockers.co.uk/showpr...=5&subcat=1344
http://www.overclockers.co.uk/showpr...d=6&subcat=793
If you wanted to go Intel, that should fit in with a £200 budget (my math might be off) and you could go to the next CPU up with small penny increase in your budget.
Or.....Again stick with the same RAM
http://www.overclockers.co.uk/showpr...d=5&subcat=326
http://www.overclockers.co.uk/showpr...d=6&subcat=793
Sorry I can't manipulate it to get an Intel Quad. Maybe someone else can.