Old entry level GPU or modern entry level GPU for retro gaming?

I have been building an XP machine from cheap listings and junk lots. I ended up with an AMD Athlon II X3, Motherboard with PCIe 2.0 and even a bluray drive. Overkill? But what I lack right now is a GPU.

What I want to play is mostly games around 1998 to 2007 games and I don't want to spend more than the equivalent of $20

For that price there are two distinct group of listings around my area: - "Newer" display adaptors like the GT710, GT620, maybe GT730 Or - Older entry level ones like the 8400GS, 9800GT, (ATI ones aren't common)

I would gladly choose the newer ones, but my concern is compatibility with the oldest games, and maybe the bluray drive, I could use this PC with WinXP Media Center. Should I go more "period correct"?