Re: which cards are better?
The 9800GX2 and the GTX 280 are about equal in performance. But considering the fact that the GX2 is about $100 cheaper, I think it's obvious which one you should go with.
iamchickenlover is right about the HD 4870 X2 though, if you want the fastest card available, that's it and by a long way.
AMD Phenom II X4 955 BE @ 4.0GHz + TU120E lapped - MSI 770-CD45 AM3 - 2x2GB OCZ DDR3 1333MHz - Sapphire HD 4870 - Samsung Spinpoint 500GB 7200RPM 16MB cache HDD - Tagan TG600-BZ Piperock - (Currently open test bed) - Windows Vista Home Premium 64bit.