Things like compression and preamping may affect bass punch, also EQ can help bring it out. Effects are spices, you should really try to start with a good sound before FX. Reverbs may muddy it up. Chorus, though, may help make it fatter.
Also, do you not get the punch, when listening to your mixed recording on a regular player, or is it just in the headphones? I once mixed a song with upright bass + ac. guitar and I thought I'd lack bass, but when I played it in my car, it was just great.
Tech 21 Bass DI Sansamp is a great box, it simulates tube amps, has EQ controls. It'll still need preamping, though.