I noticed you linked the the canadian tigerdirect.ca, where are you located that you can find a video card but not a psu? It looks like the computer will take a standard psu without issue, no proprietary psu limitations in this one.
If for some reason you like tigerdirect.ca then the Corsair 450vx is an excellent quality power supply, one of if not the best 400-500watt PSU. I have two that run 24/7 in the house and have had a single 450 power a OC'd dual core, single HDD, DVDRW, 2GB ram, and SLI 8800gt's running no problem, so carries a good kick to it:
Corsair VX450W 450-Watt ATX 120mm Fan SATA-Ready Power Supply, 80Plus CMPSU-450VX in Canada at TigerDirect.ca