Maybe it would help if you stated what card you got...
Anyhow, your assumption if most likely wrong, gatos won't bring 3d accel where there's none available ...AFAIK.
Gatos' main goal is to support multimedia features for Ati cards, mostly the Rage theater chip, but he's working off of the regular XFree tree, so what they support, he does too ...is my understanding of it anyway
.
Here's the short story for 3d accel with Ati radeons [assuming that's what you got]:
XFree-4.1.0 and up supports r100 series and relatives,
XFree-4.3.0 supports up to r200 series and relatives,
Ati's own closed source support r200 and up and everything in between.
You can get Ati's official that support up to XFree-4.2
here, but they're kinda old,
or a newer unofficial
here with versions supporting up to XFree-4.3.0.
Use the
search for radeon, it should get you plenty of usefull info.
HTH