If you're going to stick with the current iMac setup, DO NOT SUBSCRIBE TO AE CREATIVE CLOUD! It won't run on it. Instead, sniff around on eBay or someplace like that and get a copy of AE CS4, aka AE9.
Maxing out the RAM would be good, too.
Thanks, Dave- one more dumb question (sorry, I'm full of them!)- does this mean that I won't be able to subscribe to any further Adobe products on the creative cloud, as long as I'm using my current iMac setup, or does that just go for After Effectis? I'd hate to think that I have to ditch my computer, in order to ever update any Adobe products! I currently also use Adobe Illustrator and Photoshop.
I'll have to disagree with Dave. I run, correction am currently, I mean right now, rendering a project on a Mac Mini using Mavericks and it's working fine. All you have to do is add a some ram and upgrade the OS to run CC.
As you can clearly see my Mac mini is the same generation as your iMac but with a bit less power. It's not going to be as fast as a new MacPro, but with 8 or 16 (yes you can load it up) GB of ram it will do just fine. Even if you do not subscribe to CC your iMac will love more memory.
Thanks, Rick- I'll take it on by my Mac store to have them upgrade the OS and add the ram. It's worth a shot- I'd really hate to turn down a long-term project, just because I couldn't run After Effects!