New iMac

Trying to figure out the specs I want for a new iMac, mine is becomes painfully slow when doing certain tasks, especially multi-cam editing. I do a lot of wedding highlights so that would be my main type of projects.

Looking at the 21.5 inch iMac with the 2.9 processor.

Is it worth upgrading to 3.1?
Is 8gb of ram enough or should I really have 16gb? Currently working with only 4... I know it sucks.
And is a fusion drive that much better than the started drive?

In a perfect world I'd update everything, but money is tight, and I'm trying to keep the cost down when it comes to add on's I don't HAVE to have.

Any advice would be greatly appreciated. Thanks.

Yes, go for the Core i7 3.1 since it acts like an 8 core due to HyperThreading. Also, since you're considering the 21.5" get the 16 gigs of RAM because you can't replace or upgrade later (it's soldered in).

I've also considered the 27inch since the price might wash out the perspective price of the 21.5 with upgrades. I'd get a better processer and would have the option to upgrade ram down the road.

I'm considering the 27" iMac as well. I was thinking going for the new Mac Pro but the price is a bit more than I can do right now.