Rebates. Tiger drives people crazy with their fulfillment. I've bought a few things from them but ignore the rebate price. My head hurts already.
Zipzoomfly is pretty good for power supplies. They ship fedex ground for free, and since their prices are about neweggs you can save. Probably not worth splitting a 1piece order but I feel it buying several at once.
Jstrider, watch your +12v and you could save $100. If you're interested, connect a simple ammeter to your power cord, spin everything up and watch the load. Double it for sleep/startup safety and I'm betting you'll still see 375-400W. The reserve lets you do things wrong and get away with it, but that's an expensive fudge.
Just an example: My most recent RAID/HTPC box is an AMD 64 X2 4400 with 1GB, X1950Pro video, PCI Audigy, 4xWD RE 500GB drives, 2xpata boot mirror, 2xopticals, 3xcase fans (@7v), and it runs cool and quiet under 24/7 full exercised load on a $50 PSU.