Some compagny offers nicer bundle if you car about it sometimes the software can be intersting and its LEGIT!!!!
Also other vendors put some slight factory OC on their card, they can do that because they use slightly better components than specified or other things.
Finally some card have betetr coolers and more bling bling on them wich can be nice.
But as mention the most important thing when shopping for a vid card is getting a compagny that use quality components
Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-4-4-8, MSI 6800Ultra stock, 2X30gig Raid0