Hi, I don't know if this is possible in your game, but most source games support extra parameters to lower the gfx quality. You could add -dxlevel 81, -dxlevel 80 or -dxlevel 70 to lower gfx quality. I started CS:S with 70 but bumped into some texturing problems with some mods and moved to 80, but nowadays with my custom build it runs full speed. Maybe these will help you :)
