Specs question, mainly checking power supply

At the moment I'm running:
Gigabyte M57SLI-S4,
AMD Athlon 64 X2 Dual Core 4400+ (2.31GHz),
3.25GB RAM (4GB, but I'm on 32-bit XP so my graphics card and something else cuts into the total memory),
ATI Radeon X1950 Pro 512MB,
2x Western Digital 250GB HDD,
HP Lightscribe DVDRW.

I'm not sure what the PSU is as the one I bought with all the above was causing problems so it was replaced straight away and I don't know what the new one is off the top of my head.

Basically I'm going to order this 8800GT tomorrow and I wanted to check that this power supply unit is definately alright.
Preferably able to run the above rig plus two of the 8800GT cards I linked, as I may add a second in the future.

I'm fairly confident it'll be okay, but worrying about PSU specs is something fairly new to me (I always just used the case ones) and I wanted to be sure before I spend the money.

Thanks for any input.

Alright, cheers.
I read that Nvidia recommend a 600W for two cards and put my specs into a calculator site that came out as 575W, so I've gone with the Corsair 620W just to be safe.

Thanks.