Get Drumatic 2, which is free, and great for kicks.
http://www.e-phonic.com/plugins/
or
Microtonic, which isn`t free, but it`s even better.
http://www.soniccharge.com/products
or
Rhythms Bd
http://odosynths.panicnow.net/rhythms%20SA%20PAck.zip

As kicks are so important I really would make your own rather than trying to fit a sample into your track. With a kick generator you have so much more ocntrol.