XPS 700, can i put 2x GeForce 9800 GT with a 750w PSU ?

hello,   i got the XPS 700 with the 512mb GeForce 7900GTX Dual with SLI, it has the 750watt PSU, can i put in 2 of the GeForce 9800 GT 1GB dual ? they use up to 450watts, can i upgrade too a 1000watt PSU if i need too ?

The cards don't use up to 450 watts, that's a power supply wattage reccomendation for a single card system.

The 750 watt psu is more than sufficient for dual 9800 GT's. 

its me again, ok i put in 2x GeForce 9800 GT 1GB and i start playing BF2 about 10mins into the game the screen goes blank just a black screen, so i truned off SLI and it works fine, i also tried 1 video card at a time and it works fine, i only have a problem when i have them both in and SLI on, i called NIDVIA / EVGA and they said i might not have the power needed to supply them both, can you help me with this, i will get a 1000w PSU if i have too..

Power use between the 2 cards ( 9800GT and 7900GTX ) is extremely similar, Nvidia/EVGA are smoking something if they say that your power supply isn't powerful enough.

http://www.xbitlabs.com/articles/video/display/power-noise_3.html

http://www.xbitlabs.com/articles/video/display/radeon-hd4770_5.html

Your problem could have something to do with the way you installed the drivers, I'm not big on SLI, so can't be of any help there ,sorry.