According to "OpenGL Extensions Viewer 4.1.2"
Video cards that supports ATI TruForm should be these: (keep in mind that this is not confirmed !!!! )
aTI Radeon 8500
Fire GL 8x00
MOBILITY FIREGL T2e
ATI Radeon 8500
ATI Radeon X1900
ATI Radeon X600
NVIDIA GeForce 6600
NVIDIA GeForce 7600
NVIDIA GeForce 7800
About "GL_ATIX_pn_triangles" - a less amount of OpenGL games check this extension but that is trivial to fix any game (in theory) to force it work on hardware that only reports "GL_ATIX_pn_triangles" or vice versa
About "NVIDIA GeForce" - i somewhere seen that some NVidias can support it, but it not confirmed!!!
About RAGE 128 its old video card , i doubt it can support it.
I really remember ATI Radeon x550 supports ATI TruForm too.
by that any Radeon statring from 8500 and ending at X1900 should support TruForm (but its only in theory, need to be tested)
The Direct3D games now can be played With ATI TruForm technology by using dgVoodoo2