Good news: you have an AGP slot
Bad news: it only supports up to 4x
The most recent AGP cards are capable of running at 8x. I think the 4x cap is going to limit the performance you get out of a good graphics card. Have you considered getting a better motherboard? Or perhaps even a system?
Post the rest of your specs, and what you want to do with your system (i.e. games, graphics, surfing, etc).
ASUS A7N8X-E Deluxe
AMD Athlon XP 3200+
OCZ 1GB Platinum PC3200 Rev2 Dual Channel
ATI Radeon 9800 Pro
Enermax Noisetaker 485W
2 x 80GB SATA Maxtor Diamondmax 10 on RAID 0