Better graphics card for old system

So it looks like a friend is going to take my old Dell Optiplex GX270 off my hands.

His current system is:
P4 1.6 GHz
512Meg RAM (2x256Meg)
On-board graphics
Windows XP

My Dell is:
P4 2.8GHz
1Gig RAM (2x512)
Geforce FX5200 (AGP)
Windows XP

My question is, on the off chance he might want to upgrade the graphics card, what would be a better option? The Dell GX270 is a small form factor PC, so only low-profile cards will fit. The system has 1 AGP and 1 PCI slot (Note: PCI not PCI-E). Theoretically, would he be better off with an older Geforce 6200 AGP or a newer Geforce 9500GT PCI graphics card? Given that they're only playing older games, does bandwidth become an issue?

He and his wife are only playing older games (an older combat flight simulator for him and Sims or Sim2 for her). Obviously, budget is a real concern as even $300 for a new system is completely out of the question. It would probably take him a couple of months to save up enough for just the above graphics card upgrade.

-Wolf sends

the 9500GT PCI would be the better fit, its head and shoulders above the 6200 even with a p4 2.8ghz

the 6200 would have issues even with older games

PCI versions of the 9500GT

-Wolf sends

my bad.