From reading http://dri.sourceforge.net/doc/DRIuserguide.html
. It seems that 3D acceleration is only supported if the color depth is set at 16-bit. Using programs like Cadega or Wine, will always be slower than in Windows. Though it is probably best to buy video card for 3D instead using the on-board graphics for 3D.
I suggest running 'glxifo | grep -i mesa'. If anything comes up, then you are using Mesa.
People are idiots thinking GeForceFX 5200 is good. A GeForce4 is much better buy than GeForceFX 5200. I recommmend a GeForce6 6200. It much better than both GeForce4 and GeForceFX 5200. Stay away from GeForceFX cards because they are crap.