sure you can play games on a iMac why not ,
some even play crysis warhead on netbooks
http://www.youtube.com/watch?v=GqzhtI_xhPY
so anything is possible if you are determined enough
better spend the money on a Alienware area 51 ALX
intel® Core™ i7-990x (3.46GHz, 12MB, 6.4GT/sec)
6GB DDR3 SDRAM at 1866Mhz
Dual 2GB AMD Radeon™ HD 6950 CrossfireX™
1Tb ssd
and 2 nice dell 30" monitors
might be a bit more expensive then a iMac , but
that should give you enough oompf to enjoy gaming without having to wait for the next frame to turn up on display and without having to worry about settings , just slide everything to max
you did say money is no object or