From what I can tell so far, there is no way to upgrade the new 4 core to an 8 core machine. But I think I would be unlikely to do that anyway, as Tom points out it could be expensive.

It's not an easy decision to make, The price difference between the top iMac and the base Mac Pro is only £100 now. I already have a good monitor, so it's not like I really need the iMac's screen, but a dual desktop would be very nice to have.

I think what I will do is to wait for a little while and see what Apple do. It will also be very nice to see some real life tests before blowing my budget.

Cheers

Cris.