a few things:
the intel 6450 will clock as high as the 6000, and run many applications faster. you will have to overclock it though, at stock it will not be as fast as the 6000. the closest to the 6000 will be the 6600 with a pretty good overclock, or the 6750 pretty mcuh stock will beat it. you are correct, anything above the 6450 costs more than the 6000. i would love to welcome another member into the AMD family, but you should consider the intels. if you already have, fine. go for the amd as the 6000 is a marvelous cpu in any event.
you should get an 8600gts video card. it costs more, but it will be immensely better for gaming than that 8500gt. i guess that depends on how much gaming you do.
i am not sure about this, but you may want another gb of ram (make sure you buy 2 x 512mb, or another 2gb set so you will keep it in dual channel). i think vista 64-bit is going to want more ram than 2gb. someone who has vista can tell you that for sure.
the mobo you have picked out is an SLI mobo (two pcie 16 slots for two graphics cards). the psu you have selected will not power two cards, it only has one connector. if you aren't going to use SLI, its no big deal. but i would get a psu that supports it...if you come across another card for cheap SLI is awesome as long as you do not pay retail for the 2nd card.
i have the same hsf, and i love it. and its pretty.
those are my suggestions.
