GC2 and Civ4 aren't particularly demanding beyond needing support for DX9--most mid-range and up cards from the current or last generation can handle both games fine.

With PCIe, a $100 limit puts you right in the middle of the mid-range for options. NewEgg has a Radeon X1650Pro for $99.99 (there is a $10 rebate though bringing it down to $89 at the moment). That's about the best you're going to find for under $100. If you're looking to go lower, they have X1600s and some nVidia cards as well, though most of those are GeForce 7300s.

Personally, I'd sooner go with a card of an older generation that's in the 600 or 800 series (or better) than one of a newer generation that is not. The 600 series cards from both companies are the standard mid-range models, and performance-wise (though not necissarily feature-wise), the last generation's 600-series cards are often superior to the sub-600 cards of the newer generation. In practical terms, a GeForce 6600 is faster than a 7300, and a Radeon X800 is faster than a X1300, though all other factors considered the prices are similar.

Thanks Kryo for the help, I really appreciate it.

I found a GeForce 7600GT 256MB at New Egg for 99.00 after rebates....is that a better card than the X1650?

The reason I ask is because I looked at Wikipedia and it said that the 7600GT was marginally better than the X1650.

http://www.newegg.com/Product/Product.asp?Item=N82E16814141043