I recently bought the 27" iMac with an i7 processor, 8GB RAM, 2GB Video Card, and the SSD option. (My configuration is close to, but not quite at the top end of the line.)
It's blazingly fast, and I do some pretty heavy work with large datasets and virtualization.
I don't think you'll be disappointed with this model at all.
Here's a simple way to look at it:
WAIT A BIT IF: To achieve what you want, you need the most expensive model, with the very highest clock speed, maximum RAM, SSD, etc. If so, then you are going to be paying a premium for the cutting edge of technology. It probably makes sense to wait an iteration so that the price on those high end options will come down. (of course there will be a new round of higher end options by then.)
BUY NOW IF: To achieve what you want, you need a model with one or two features maxed out (like fastest clock speed, or highest end video card). With this mixed configuration, then you're paying a more reasonable price for the specific things that will help you achieve your goals. Even if a new model comes out with other options -- your cost savings may only amount to $100 or $200... It would have been better to buy the computer earlier for that small difference.