Do I Need A New Power Supply For A New Video Card??

I'm looking at getting one of these:

BFG Geforce 6800 GT OC 256mb
BFG Geforce 6800 GT OC 128mb
ATI Radeon X800 PRO 256mb
These can be found on Best Buy's website, thats where it probably will be coming from.

My power supply says max 270w, so do I need a new one with more juice? Or will this one do for one of these Video Cards?

Power Supply:
NMB
Model Number - MJPC-270A1

Specs:
Sony Vaio RX881
P4 2.66ghz
512mb 2100 DDR
120gb 7200rpm HD

No upgrades, stock as it came. No overclocking or anything.

Thanks :suspiciou

I believe that a powerfull processor like your needs about 100watts of power to run. Every 128megs of ram = something like 15watts, and your cd drives are about 30 each. A powerfull video card can run in the range of 100 watts as well. So, you do the math. It's time for your new power supply as well. You should at least have a 300watt but, with your processor i would even go to a 400 watt. Spend the extra 15 bucks, might save you a big headache in the end.

Alrighty, thanks.