The Right iMac for SC2?

I thinking of getting one of the newer iMacs to run StarCraft 2 and do video editting and I was wondering if the best 21.5" model is capable of running SC2 well (at, like, the medium or better graphics settings), as well as possibly other computer games (L4D2, Portal, etc.)

3.2 GHz Intel Core i3
4GB RAM
ATI Radeon 5670 512 VRAM

Should I get this or just wait and save up for the $1999.00 27" model?

You shouldn't have any problems for those games, probably be able to use them at the high settings too.

- Simon