If you say exactly $200, I can find some good deals for you currently (or you can save the trouble and check NewEgg yourself!).
Even a difference of $20 can make a difference when it comes to VGA cards in terms of what you can buy.
If you find a GREAT deal at NewEgg, try to find a Radeon HD4850 for around $150.
It will probably require a mail in rebate at that price, so it's not the initial price you'll be running on your credit card.
Typically, when I'm sourcing parts, I try NOT to count the rebate as a part of the build price since rebates often take a long time to process, and sometimes don't get approved (currently waiting on a $40 rebate for a HD4870 that would be a great bargain at $225 w/ rebate).
As for RAM, I've seen DDR2 8500 (1066mhz) 2x2GB kits going for under $50. If you can score a deal like that, you're set, even if you are using a 32bit OS that won't address the whole allotment (at that price, who cares?!).







