need help on graphics card

Is it PCI or pCI-e? Most probably its PCi along with AGP. AGP is much better and offers larger bandwidth for data-transfer than a PCI card. Though AGP is also in its dying stages(being replaced by PCI-e), still its much better than PCI.
Best AGP cards avaialbel today are the 7800 GS and 7600 GS fron nVidia and X1300 from ATi. Though the nVidia cards are nice, but they are priced too high. X1300 is the cheaper alternative

PCI (Peripheral Component Interconnect Bus)
Pins / Data Bus /Address Bus /Transfer Rate /Speed
124 /32 bits /32 bits /132MBs / 33 MHz

AGP (Accelerated Graphics Port)
Pins /Data Bus /Address Bus /Transfer Rate /Speed
188 /32 bits /32 bits /264MBs / 66 MHz

AGP is better than PCI

AGP (Accelerated Graphics Port) cards serve the same purpose as PCI graphics cards. However, the AGP interface, which was created by our buddies at Intel, has become the more popular choice for PCs. Part of the reason for this is that AGP cards manage memory better than PCI cards. The AGP interface can actually use your computer's standard memory as well as the video memory to help boost video performance. So, if you have an AGP slot in your computer, I'd go with an AGP card. If you only have PCI slots, however, a PCI graphics card isn't going to be much different.
Hence, go for an AGP card,which will provide you with excellent sideband addressing mode.
By the way,mention you motherboard name accurately,so that i can provide you thorough information.