good god man.....if it means playing the sims2 THAT much to you...then you need to do some investigative work on what you got and what you can upgrade....read about benchmarks and that sort of thing. PCI based graphics cards are gonna suck compared to AGP....no doubt about it...if you're gonna get a PCI card you need to get the highest memory on it possible...don't get 64mb if you can get 128mb...you need all the help you can get. You need to get another stick of ram...period..whether it be another 256 or a 512 or what you need more ram...ATLEAST another 256mb stick.
I believe thats the graphics aperture size...you can raise that a little...but you need to get more RAM because the graphics aperture is just the amount of RAM set to help out in the event that the video cards VRAM is full...which will happen quickly on a 64mb card hence furthermore why you should atleast get a 128mb card if you're gonna get PCI.
Get more ram - atleast 256mb
get atleast 128mb card if you're going PCI video card
Change Graphics Aperture size in Bios from 64 to like....128 with current ram and 256 if you wind up getting more.