You have 320mb. It's not bad, but it could be better as there was a 640mb version. Both those cards only have 96 shaders so they will perform worse than the 8800GTS 512 as that version has a full 128 shaders. If you want to play Crysis 2 you may experience a good bit of slowdown simply because 320mb isn't enough RAM so the system will spend a good bit of time swapping data in and out of the card even on lower settings.
but I got this card for 8 pounds so I just bought it
also, Im thinking of getting an aftermarket cooler, apparently 8800 coolers suck
is accelero l2 a good choice ?
The stock cooler is o.k. For that price I'd say you got a great deal ^_^. I wouldn't really bother with a better cooler unless the airflow in your case is rather poor.