You definitely want hardware acceleration if you are going to play
games. This is provided by the DRI module. First check your XF86Config
file under: Section "Module" there should be and entry Load "DRI" there
should also be another entry load "glx". If they are there then tail the
/var/log/XFree86.0.log file following system start up.  You should see a
message such as Direct rendering enabled.  If not then DRI is configured
but failing for some reason.  Should be an error message in the in the
same log.  If you do not have it I would suggest you begin by going to
http://dri.sourceforge.net/ and looking at the documentation section. 
There is a DRI beginners guide and a DRI user guide.  The documentation
will talk about MTRR and AGP.  in RH 7.1 and 7.2 these things are
already enabled.  No need to compile the kernel.  VOODOO3 should work
with XFree86-4.1  Of course I got the same sense about the ATI card but
I finally ended up with XFree86-4.2 which got a lot more complicated. 
Let us know how it goes.  
-- 
Paul Overby
xpoverby at attbi.com