Thanks guys!
Just tried all sorts of things and benchmarks with 3DMark03, here's the results:
GPU @ Stock & Graphics @ Stock - 7,621 (CPU got 373, lol)
GPU o/clocked & Graphics o/clocked - 8,530 (CPU still only got 429, lol)
As above, with the Omega drivers - 8,509
So quite a nice performance boost from overclocking, my FPS in Counter Strike Source also shot from very choppy to a stable 35fps which is nice, especially since I'm running it at 1680 x 1050 in full detail on a pretty naff PC
Not too impressed with the Omega drivers, Half-Life ran very slightly better but 3D Mark in particular seemed to come off a tad worse, but most importantly it crashed a few times too and threw up some weird error messages, so I went back to the standard ATI drivers!
My only concern is that the CPU is running at around 65 degrees under load, it's an AMD Barton so should go up to 85 I think before it starts getting into trouble, but 65 degrees still seems quite high; should I underclock it/whack the fan speed up or should be alright?