Couple of graphic card questions

I just had a couple of questions about current graphics cards. I'm looking to upgrade my system, and looking at some of Nvidia's latest offerings. However, I'm concerned that they're only DX10. Is that a big deal? Is it possible to upgrade them to DX10.1 with a software patch (thats probably a really stupid question, but hey). Also, is there any difference between the brands? What's the difference between a 8800GTX from say, BFG, EVGA, XFX, etc. if any?

Ok, i had to change my post, Currently the 9800GTX is cheaper than the 8800GTX's on newegg. And with the exception of a couple resolutions/settings beats the 8800GTX. But Also in that same respect, for a good bit less, the 8800GTS 512mb does darn near the same thing, Tying or beating the GTX(8)

So pick a card, either 9800GTX or 8800GTS 512 as they are very close to being the same card. And let the 8800GTX die with respect

http://www.newegg.com/Product/Prod [...] 6814130339 (EVGA 9800 $299)

http://www.newegg.com/Product/Prod [...] 6814134037 (ECS 8800GTS 512 $219)

http://www.newegg.com/Product/Prod [...] 6814127325 (MSI 8800GTS 512 OC $224)

I have the latter, its a great card does well, Specs in sig, it beats my friends 8800GTX/ E6750 @ 3.0ghz. And 6gb of ram and comes OC'd.