By the way, if you already own the mac pro (noted dead gpu line) then I'd stick with that. I just wouldn't necessarily buy a mac pro 3,1 with unknown history today. Dead gpus seem to be a common complaint with that one. An ssd isn't a bad idea here. That model had expensive ram. While ram is the fastest, an ssd can also be used to hasten scratch disks if you're dealing with a long history palette + large files.
Illustrator can be annoying, and it doesn't scale well at all. Most stuff in photoshop takes advantage of around 4 cores. It's not like it can never put more into use, but the returns fall off a cliff past 4. The 4 in the newer imacs, especially the 27" i7 are significantly faster per core. I could understand not wanting to get a new one with mountain lion. At this point it's kind of an unknown, and it will most likely take some time for bug fixes.
Don't pay attention to the rumors. They are often bad information. There's very little reason for it to slip that late if it's just the typical refresh, which is what I'd expect.
You don't seem to understand this stuff very well. The imac is technically faster for what you're doing. Overall ram is cheaper. Go with a minimum of 16GB. You can even go 32. The point is not to hit scratch disks in these applications. They scale horribly beyond 4 cores. I'm not sure if the 2008 model gpus are supported for gpu acceleration. It's not worth upgrading as it only pertains to a couple functions, but ideally you want that as it hastens a few actions by a large margin if you use them. I wouldn't go with the 2008 unless you find a really good deal on one. It's old, and it's not likely to be supported forever. Apple sort of has to support 2009 and later because they still sell what is essentially that machine. If I was going to bring up counter points to the imac here, none of them would be an issue of processing power. also the 2008 mac pro uses expensive ram. Make sure you look up the total cost of any potential upgrades before buying one.
