What's your reason for i7? If you will sell the whole rig and get a new one after a few years, you can get by with LGA775. i.e. Q9550 ($300 CAD on sale; you missed it out), P45, DDR2-800.
Ok, I read your 2nd post. For video encoding, i7 is worth every buck. From what I've read, the P2 955 is pretty good at gaming.
IMO, the usage you mentioned don't warranty i7 or Phenom II. Any fast AM2 or LGA775 setup will suffice. The only reason for me would be upgradability. The last x2 s775 would be E8600. Some already call LGA775 a dead platform. It doesn't mean the cpus will disappear from the surface of earth. They will be around for a long while. Especially on ebay. AM2 still has some life in it. It can run AM3 cpus minus the DDR3 memory controller. Personally, I'd wait for AM3 to mature before getting a board. Like fall/winter. Also, i5/P55 is coming this Oct. It's the mainstream platform, unlike i7 the premium. So if i were you, I'd get either AM2/LGA775 for now and wait for the dust to settle down before going to the next platform.