I have an HP p6703w, the current power supply in the machine is:

Bestec ATX-250-12Z-D7R
P/N 5188-2622

+12v/14a
-12v/0.8a
+5v/25a
+5vsb/2a
+3.3v/18a
20 pin, even though the board has 24 pins...

I'm looking anywhere between 500-600 watts. I have 250 watts now, which seems too low for the hardware it's already powering, let alone a new video card. The only power supplies I've found were 400 watts and below.

The last PSU I bought...the fans and motherboard light came on, but the standby light didn't and the computer did absolutely nothing from there. ;

Due to small complications with my bank not matching my shipping address, I'd like to do eBay if possible...but I can work around it if I have to.