Should this be a big concern, i'm planning to get a board tat is compatible with Hybrid Crossfire, but I'm planning to get a nvidia gfx card(gtx 260 core 216) should this make a difference, that i should change to ATI gfx cards. If so, which one for under $250
More abouthybrid hybrid crossfire
The nVidia card will work just fine (but of course you won't be able to use Crossfire).
Like Mondoman said you don't have to go for a ATI card... If you want an alternate option for a GTX260, go for the 4870 1GB... Both perform neck to neck(In few cases, the GTX is powerful)... But you can get the 4870 for about $30 less than the GTX...
Both hybride crossifre and sli have rather limited usability as they work with limited (low-mid range) cards. Just go discrete (260-216 or 4870) and don't worry about it at all