The difference between mat_picmip 0 and -10 is immense!
Since TF2 is very CPU-limited, every half-decent GFX is enough to max the settings out. Copy this to your autoexec.cfg (and adjust as you see fit

):
These are all pretty much "free" in terms of fps decrease.
cl_new_impact_effects 1 //Fancy particle-effects
cl_burninggibs 1 // Guess what
mat_motion_blur_strength 2 //More motion-blur!
mat_motion_blur_forward_enabled 0 // Set to 1 if you like it. I don't.
The following might slow you down a bit, I listed what part needs to be fast.
mat_picmip -10 //Sharper textures (GFX, Vram, Ram)
mp_usehwmmodels 1 //Detailed models (CPU)
mp_usehwmvcds 1 //Detailed facial animations (CPU)
r_lod 0 //Disable level-of-detail (CPU&GFX)