That's an alarming amount of shipping and tax. Since you're in Canada, I suggest checking prices at NCIX
too before you buy.
I would go with a 7200rpm hard drive if that's going to be your only storage device; hard drives are cheap these days. If you're bringing over a 7200rpm drive from your current machine to use as a boot/system drive, the hdd you listed will be fine as a mass storage drive.
That 6870 seems a little out of place. Depending on your monitor's resolution, you may be better off saving $20 and dropping to a 6850, or even further to a 5770/6770 (they're the same chip).
8GB of ram is nice if you can swing it, but 4GB (as a 2x2GB kit) should be enough for your intended purpose and a small to moderate amount of background tasks. I didn't have many problems playing TF2 on max settings with 200+ tabs open in 3 browsers when I was running 4GB.
I second (third?) waiting a few weeks until Bulldozer comes out. Even if it turns out to be outside your price range, it should drive down prices on the Phenom IIs you're looking at. Awesomeguy, Bulldozer is a major architectural change, on the same order as Intel dropping Netburst in favor of Core.
Keep in mind, vcordie, that overclocks are not at all guaranteed. I have an X4-955BE, and mine isn't prime95-stable at 3.6GHz, let alone 4GHz. On a semi-related note, Harok, faster RAM doesn't matter much here, because the memory controller in these CPUs usually won't run DDR3-1600 at 1600MHz.
An SSD for a boot drive would be nice, but I don't think you can squeeze it in without breaking your budget.