Source engine typically only requires DX8.1 hardware (it can drop to 7 if you don't mind it looking crap), and has a few DX9 features as an option extra.
In hardware terms - Minimum is a T&L era card (DX7/1999) for ugly mode, shader 1.3/1.4 card for standard (DX8.x), and optional effects sat on shader 2.0/3.0(DX9/9c).
(Note - later Source games removed the ugly & standard modes, instead requiring the DX9 level hardware)
Toribash's shader system requires 2.0 for the basic stuff, 3.0 for everything to be fully functional.
This is where people start with the "xxx game looks better so I should be able to run this..." NO, NO NO NO! That's not how hardware works.
Shader requirements are based on the number of instructions a vertex/pixel shader has. Simply put, the shaders in Toribash are far more complex than the ones in games you're able to run. Nothing to do with poly counts, or any of the other guff people tend to bring up, it's purely down to maths and the hardware's ability to do it.
Hope that explains.