When using the drum replacement make sure you tell logic it is a kick or a snare or whatever so midi is on correct note.
Once you adjust sensitivity and convert to midi, open the midi editor and use the line tool to draw a straight line across the velocities at about 100.
Velocities are all over the place with the logic drum replacement.
Open a default EXS24 sampler and go into edit mode.
Drag you kick sample onto the edit window then select it to be one shot and not follow pitch.
Make sure you put the sample on the C1 key (for kick) or D1 (for snare)
Should work.
If it doesn't post back and I will try to help more.