How can I tell if it is stock or factory overclocked? and how can I find out what kind of cooling it uses?
Last, does the amount of gigabytes mean anything? I read somewhere in an article that there were other more important aspects of a card than simply the amount of gigs advertised.
the stock clocks on a 5870 are 850/1200. The reference cooling looks like this http://mos.futurenet.com/techradar/Review%20images/TechRadar/Computing/5870/ATrHD5870_angle5_md-420-90.jpg
if it has a different type of fan on it then it is a third party. 1GB on the cards is going to be enough unless you are going to be running 3 monitors @ 7680x1600.