IMO, SLI or X1900XT are both good options. But the real question is how much will you gain by doing a vidcard upgrade? How fast is the rest of your system? Which racing sim is it that you need it for? What resolution are you running, that you need a video upgrade?
BTW a 500W Enermax will handle a single X1900XT or 7900 SLI with no problem at all. What I would do is wait a few weeks for the new 7950 GT - should be a great card - or, if you want some more, wait a bit more for the new X1950 XTX. Most of the time, single-card >> dual-card, in terms of price-performance.
BTW a 500W Enermax will handle a single X1900XT or 7900 SLI with no problem at all. What I would do is wait a few weeks for the new 7950 GT - should be a great card - or, if you want some more, wait a bit more for the new X1950 XTX. Most of the time, single-card >> dual-card, in terms of price-performance.