If i buy xfx 8600 gt xxx video card will i have to buy sli powersupply?

I have an Acer T180 vista home prem.I was wanting to upgrade my graphics with XFX 8600 GT XXX video card.I will need a power supply too,because it is 250w. my Question is if I buy this video card will I have to buy SLI power supply too?OR would any over 350w work?|||Get a 400W power supply or better, and no, you do not need a SLI Powersupply unless you are going to run two graphics cards