? on specs for Civ 5

Hi there,
I am currently shopping for an iMac. Wife and I will be using it for
-light to moderate picture editing
-surfing web
-school work after the summer months
-finances
-watching/streaming video/music
-light gaming

I really only play one or 2 computer games; Sims and Civilization. I am more concerned about the second one, its been out for mac for a while now -Civ 5 that is- and here are the specs to run it
---Minimum Mac System Requirements:
•Operating System: 10.6.4 (Snow Leopard)
•CPU Processor: Intel Core 2 Duo (Dual-Core)
•CPU Speed: 2.4 GHz
•Memory: 2 GB RAM
•Hard Disk Space: 8 GB
•Video Card (ATI): Radeon HD2600
•Video Card (NVidia): Geforce 8600
•Video Memory (VRam): 256 MB
---Recommended Mac System Requirements
•CPU Processor: Intel Quad Core
•CPU Speed: 2.6 GHz
•Memory: 4 GB RAM
•Video Memory (VRam): 512MB

My ? is, is anybody having issues running Civ 5 using an ATI Radeon HD 4670-256MB GDDR3 SDRAM video card set up? Also,we're to get the iMac from bestbuy with some giftcards we have saved up and they only offer a few models.
Apple®iMac® / Intel® Core™ i3 Processor 3.06/ 21.5" Display / 4GB Memory / 500GB Hard Drive
and
Apple®iMac® / Intel® Core™ i3 Processor 3.2/ 21.5" Display / 4GB Memory / 1TB Hard Drive
Since ram is not an issue currently, the CPU increase is not a must, and 500g/1T is not a concern either since i have an external.

THe difference b/w the 2 models is 300$. Money is tight and since the only thing that will be done on the iMac that will be affected notacably would be the 3D gaming.

Any input?

You should have no problems

I have played the civ5 demo on Steam with no issues. I played it on a mid '09 MBP, 2.53 GHz Core 2 Duo P8700, 8Gb Ram, and an NVidia 9400M gpu. The game ran no problems on low settings so the iMac you are looking at should handle the game with ease. You might try the website Game-Debate.com for a little more reassurance. They have a system checker where you enter your rigs specs and it will tell you if you can run a game or not. Just be aware that the results are based on the "recommended" hardware specifications and not the minimum. Systemrequirementslabs.com has a feature where it scans your rig and tells you if you can run a game or not. Of course since you do not have the iMac yet this is not an option. Systemrequirementslabs.com yields more accurate results based on BOTH minimum and recommended specs. Game-debates results said I could not run BFBC2 while Systemrequirementslabs said I could. Systemrequirentslabs was right on the money and I play online everyday now. I run my games in bootcamp and do not know if systemrequirementslabs features work for OS X.

you should be fine with either imac.