Definetely do NOT buy a Geforce 5200. Even though it's a new card which supports Direct X 9, it performs HORRIBLY.
The ti4200 is a good card, I sold mine to a friend this summer in order to attain funds to buya radeon 9800. The ti4200 64 meg was still performing well, but I wanted something with a more powerful chipset and memory speed. In your case I would definetly recommend saving another $50 like Finchie said and getting a 9600 Pro.
Another thing you should know is that just because a video card has 128 megs of RAM doesn't make it fast. There are numerous other things to consider as well. The main factor is the video processor on the chip and how many calculations it can perform, how well it handles pixel shading etc etc. Also you want to look at the speed of the RAM and how big the interface between the RAM and the graphics processor is. You really should do your homework before buying a video card because there are so many things to take into account.
You should visit
www.tomshardware.com for some excellent video card reviews that will help you with the purchase.