The requirement rig for modern pc gaming really isn't that complicated and don't believe some hype you read over certain components. Ofcourse more $$ means prettier gaming but thats life....$$.
Assuming you are not made of cash but are willing to pay a fair amount heres some simple points in non tech talk:
CPU
- Avoid quad cores, you can get more power for your $$ when gaming on all dual-cores tbh. Games are almost non existent that fully utilise 4 cores that it really isnt worth the $$ if oyu are on a budget
Memory
- Ram is important, and cheap. Get atleast 3GB+. If you are on a budget dont pay for overpriced RAM that costs $400 for the same GB's. Yes its better ram (it costs more) but you can save money here. However, don't skimp big time and buy self branded RAM from Wallmart or Macdonalds. Brand does matter with important electronics if you want you're purchase to not live a short life. E.G - corsair is good RAM brand.
Graphics
- The most important component for gaming. Although all components have a role to play in the stability of a game, graphics determines how well it runs on those pretty graphics. Personally I don't ever skimp here, if you are planning on spending $700+ on a rig the biggest portion of $$ should be on graphics, you can get top GFX nowadays for 200$ or slightly less even. Yes you can pay $1000+ for top of the range but hey, we aint Bill Gates.
BTW - SLI graphics is not a requirement for running a damn game in top GFX. Infact, alot of the time unless you are rich it really is not worth the cash. Just do research on these things before you buy. tomshardware and such are great websites for learning whats worth it and whats not. E.G. Sometimes its a cheaper option or much better value to actually run older cards in SLI than to run a very recent a new card on its own
I can't be bothered to go into every little component required to make the above things actually "work" but one more thing worth mentioning is your PSU or powersupply. Just make sure it has enough spunk to run your gizmo's and dont buy unknown brands. A selfbranded Wallmart PSU will simply die at some point and take all your expensive components with it. Trust me, pay a little more.
I don't really know why I wrote this all out and it has nothing to do with Civ 5 specifically, there just seems to be alot of people here who are surprised they cant run a modern game with good stability when they have a "brand new PC" with intergrated $50 graphics
.
All I can comment on is my experience from playing this game on max settings.
I run 3GHZ dual core, 4GB DDR2 RAM, and a HD5770 ATI Card. It runs very smoothly. The only reason some parts of this game don't run smoothly is all to blame on the game. My friend has a $3000 rig, and his turns still take forever to pass so there you go