I am about to purchase the iMac. I was wondering about ATI Radeon HD 4670?

Ok..so let me tell you...I have the same graphic card but the 1 gb version, the one which is on iMac is of 256mb (assuming you are getting the 21 inch mac). The card is pretty gr8...it has one of the best price/performance ratio in the market...it can play a lot of games.... well, like I can play assassin's creed at highest settings with little anti-aliasing, and nba 2k10 also at highest settings. But don't expect too much out if it for example playing crysis at highest settings in a good resolution.... It's still a very nice card for the price and displays graphics in superb quality. But since you are getting it in a mac there's no point thinking over its price/performance ratio.... Instead I recommend that you get yourself a custom build. You can get a much better graphics card and a better processor than the ones with iMac under about half the price. It will be a good computer but unless you are very specific to getting a mac... I would tell you to build your own PC, it will surely be more powerful. Again remember the gfx card that's in the mac has only 256mb so that could be a big drawback. All the best.