[quote name='dl402']but I want the ones with the new heatsinks or chips or whatever.[/quote]
Well, if you're wanting one with the new chipset, you'll have to miss Halo 3's release. Because the models with the new chipsets have not been released. All that's been mention is they'll be released in Fall 2007, nothing else.
As for cheapest, Gamestop has a core system w/ wired controller for $189.99 used.