A GT250 is a 9800GTX, its slightly upgraded and uses less power
but works just fine with EFI strings for a 9800GTX, and is even detected
and usable without EFI strings, using "PC EFI 10.5" and its GraphicsEnabler

As far as getting parts for a Hackintosh

(1) Stick with Intel and Nvidia

(2) Stick with dual DVI video card, name brand

(3) Get a name brand, well reviewed, power supply

(4) Get a motherboard know to work, that there is a guide
for, like the "GA-EP45-UD3P" and others, that will cut
out 90% of the problems