First off, ya gotta be sampling kicks that have a solid low end. do you have a DAW or anything? you could use a spectral analyzer to see what frequency range the kicks you are using have.
using the MPC effects, you can do a couple things for kicks. you can use the EQ effect to turn up the gain on the low end. you can use the compressor effect in there to compress your kicks.
layering different kicks, especially combining kicks that fill out different ranges of the frequency spectrum, will also help make yr kicks sound more full
