Currently I have a Antec TruePower Trio 550 PSU and a Nvidia 7900GT PCI-E. What could I reasonably expect to upgrade to (within the Nvidia card family) with my current PSU? I know how to replace PSU's, but I find it a pain and keep from doing so unless absolutely necessary. Also, this is all inside a Midsized Tower http://www.svc.com/cac-t05-uw.html