A
quality 550 psu is plenty for even overclocked dual card rigs. Good power supplies are rated at their sustaned wattage, not short 10 second spike wattage like some cheap PSUs. My powerstream 520 doesnt even hiccup with dual overclocked x1900XTs, tons of high cfm fans, 1ghz cpu oc, two harddrives, cdrom, burner, lights, etc etc. All on a single 12v rail. It is 60 second rated at 650watts peak load - I bet thats enough to be labled as a cheapo 700 watter, even though it was released as a 520.
It may be a gen or two behind, but it proves that a good quality psu can handle a lot more then most people would think.
80mm fans can easily be fixed with a dremel