You don't need a new power supply for these cards The Antec basiq model isn't really that good either. Their earthwatts 380 would be as good and higher quality.
And you won't find an 8500GT very good for gaming. Even the $40 HD2600 pro above is better. For the price, you could have a HD2600XT that sit's above the 8600GT never mind the 8500GT. That said, for buy it today and no rebates, bring it back if you don't like it, etc. .... the cicuit city price is respectable for a retail chain. Problem is it is not a good gaming card.
Keep in mind Neweggs shipping is very quick depending on your state. I ordered a XFX 8800GS for $90 AR with Call of duty 4, shipped free on Wednesday morning. I would have recommended that but it's too much for your power supply. It arrived yesterday, less than 30 hours after I ordered. Most people get their stuff in two days if the closest warehouse has them. If not it will take a third day.
edit: if there is a problem, you have to ship it back though.
edit again: another thought. The evga 8500GT would let you use it today, be returnable to the store if you are not happy, and also worth mentioning it can be used as an upgrade on evga's tradeup program. You'd get the full $80 put toward another card if you trade up within 90 days. Not always or even typically a good route to go, but just wanted to mention it is a possibility for your consideration, since you want a card today.