A 450W FSP AX-450 (dual +12V at 18A each) will work perfectly fine, and you'll save some cash. Your graphics card is pretty undemanding in terms of power usage (doesn't even need separate PCIe power), and you aren't running a lot of other accessories and parts such as a RAID-5 setup or anything like that. So a $100 PSU isn't really necessary for your system unless you plan to upgrade a lot of parts in the future and want to keep the same PSU. Many people on AT tend to suggest high-priced PSUs since they are the "heart of your system," but I really don't see the need for getting an expensive, high-end PSU when a solid Fortron unit will work just fine for your relatively undemanding system.
Just so you know, I have personally been running a FSP AX-400 (the 400W version of what I'm recommending to you) with my the setup in my sig for about a year now with absolutely zero problems. A friend of mine has the same PSU in his rig (X2 3800+ @ 2.5, X800GTO^2 unlocked and OC'd to X850XT PE levels, dual HDDs), and he hasn't had any PSU issues either. Another friend of mine built a C2D rig in late 2006 with a FSP AX-450 (E6300, X1900AIW) and also hasn't had any PSU problems.