AE should run on pretty much any of those Macs, but you get what you pay for - depending on how it is outfitted with CPU, RAM and graphics, rendering times may not be that great and the notorious heat problems with some graphics cards will spoil the fun with crashes. CS4 is able to detect HT CPUs and will report them correctly, but it only uses physical cores, if I recall correctly (it definitely does so on the PC, but I'm not 100% sure about Mac). But it really depends what you do. "Spots for local outlets" doesn't really mean much - they could still all be HD (AVCHD/ HDV/DVCPro) and be full of render intense effects, making your iMac glow in the dark...
Sorry...all HD for the most part. Also, hadn't thought of the heat issue. I'm torn. Don't want to buy more than I need, but don't want to buy something that might be underpowered.
I think those mac are perfectly suited for professional work. They are pretty fast and if you boost the RAM, you will have a great workhorse