New Graphics Card

Hi,

I am looking to buy a new graphics card this summer ready for university and I want a rough idea of what to buy so I also know how much to save up.

Im looking to spend roughly £300 ($550).

Ive seen these SLI compatible cards which sound pretty impressive with demanding games like Doom 3 or would it be better to get a single ATi card like the 9800 XT?
Also, does anyone know if ATi are goint to do SLi style cards in the near future because I wouldnt mind waiting untill like xmas time as Im sure i will get my money's worth with them, as I prefer ATi usually.
If not could someone recommend 2 gud cards for SLi with nvidia's, ive seen couple 6600 GT's (not ultra ones) available on ebay within my price range.

Any comments would be great,

Thanx