Re: BFG GTX 260 OC or BFG GTX 280?
They have to account for a margin of safety. Not all PSU's are created equal. Its mostly about how many AMPS your PSU makes not WATTS... however no one looks at amps. Thus parts companies need to go off of Watts, which is all fine and good but like I said the AMPS created aren't always going to be equal even if the watts are.
Simply put, a 500W PSU with a good amp to watt ratio can and probably will run a card with a minimum 650W PSU requirement... however if they stated 500W as the "minimum" you would get a lot of people with lower performing PSUs blowing their cards, then bingo they get stuck with thousands of RMAs.
Think about that.
Ultra M998 mid-ATX case
SilenX 650W 14dB SLI Power Supply Unit
Nvidia/EVGA 780i tri-SLi motherboard
Intel Q6600 quad core @ 3.4GHz (3.6 for benchmarking)
2GB OCZ ReaperX HPC Edition PC9200 DDR2 RAM (2x1GB)
2x EVGA 9600GT SC in SLI (750/1100Mhz over-clock)
2x WD Raptor HDD (1x 36GB; 1x 74GB)
Samsung Spinpoint HDD (250GB)
Thermalright TRUE-120 w/ dual 120mm fans in push-pull config.
Windows Vista Home Professional w/ SP1 (32-bit)
Samsung SyncMaster 206BW 20" LCD display (1680x1050)
3DMark06: 17,420 Points