just be aware that the second pci-e is limited to x4 operation when the first slot is filled. so even though its advertised as sli complient its really only meant for 2 low end cards 2 high end 1s require x8+x8 pci-e support to ensure smooth operation.
also no mention of your cpu. i hope its a quad core as thats minimum requirements for new AAA titles today.
forgot to add do you have the required output from the psu... minimum recommended is 500w if its a pre built system its likely to only have 350-400w psu which will likely not be enough.