in all reality if you are building for the games you listed, but you do video editing on the side, you should still go with intel for that. you won't notice a difference in those games with that video regardless if you went amd or intel.
i am not a intel fanboy as i usually build amd machines, but the rig in my sig was built about 1.25 years ago with video editing/encoding in mind and it has excelled at that. encoding is where it reall shines, and to be honest, is not too much slower in games than a friend of mines a64 3000 w/ 6600GT in 3dmark 01, 03 and 05 (not that these are the best benchmark), playing bf1942 w/mods we both use the same settings and you really can't tell them arpart. his higher speeds i am assuming are directly related to the video card.
the dilema is that the new intel stuff is pretty expensive compared to the amd.
if you go amd though, go with a different board, i have talked to a lot of people lately about those dfi boards and althougt they kick @$$, they are ram finicky. the ones that work fly, but there seems to be quite a bit that don't wor well.
also, i would go with a .09 a64 3000 because the new dual core cpus will be out soon and in about a year will be reasonable in price, then your machine would be excellent for encoding. imo, spending $340 on a cpu for "future proofing" is a bad idea because that chip will be worth 1/2 in 6mos. imo you would be better off with a better video card since that would be your weak point in a year or two if you go other games, or just stick with the 6600GT, which is an awesome card and save ~$200.
you say you want lots and lots of speed, but in all reality with todays computers the problem is the hdd. if you want the machine to feel faster, i would go with a raptor and then a large secondary hdd for your video. chaning the hdd to a 74GB raptor will definately make the computer respond much quicker and will "feel" faster.
so, the changes i would make would be a different nf4 based m/b, a 74GB raptor, keep the 250GBhdd and go with a a64 3000 and you will still have a kick @$$ computer, then when the dual cores are reasonable, do the bios updated and buy one of them