Does it matter what agp card I am getting? I see graphic card that are DDR DDR2 DDR3 etc. Right now I am using a agp ddr graphic card Nvidia Geforce FX5200 128mb and I was wondering if I can get an upgrade for a card that is agp 512mb+ ddr2 or ddr3.
Probably the best AGP card you can get right now is the Radeon HD3850: DDR3 and 256-bit interface are both really nice features. However, it sucks up a good deal of power and requires an 8-pin (or 6+2 pin) PCIe power connector, which a lot of older power supplies don't have. So check your power supply and make sure it's up to the task.
If the HD3850 card is going to be too demanding, they also have the HD4650 and HD4670 in AGP format; they're both lower power consumption but only 128-bit interface ... the 4650 uses DDR2 and the 4670 uses DDR3, so maybe worth a few extra bucks.
The reality is that in an older machine, you probably won't get wildly different results between any of these three cards. They'll all be a nice upgrade that basically maxes out what your system can do, and other things like your CPU or RAM, or even simply the data transfer rate of the AGP interface will become the limiting factor. In other words, no card is going to make your old AGP machine into a high-end gaming rig, but it'll keep it relevant. The biggest upgrade (I thought) was having things like DirectX 10 and Shader 4.0 support -- a lot of old graphics cards are stuck on DX9 or Shader 2, which won't even let you run a lot of new games.
Also, if this was your question: It doesn't matter what kind of memory your old graphics card used or your motherboard uses. Video card memory is completely separate from motherboard memory and there won't be conflicts. You can have a motherboard running DDR and a graphics card running DDR3 if you want and you shouldn't have any compatibility problems.
Oh, also: From what I've heard, avoid buying anything from PowerColor at all costs. They take "Made in China" to a whole new level.
Sapphire has a pretty good reputation, and a lot of people like XFX (which has a lifetime warranty on most products). You probably won't go wrong with Gigabyte or ASUS, although I know them more as motherboard makers.