Re: tempos (bpm's)
yeah, your best bet for finding a close enough tempo for an a capella in Acid is to:
beat-map the original, set your project tempo to it and lay down the a capella under it and sync the down-beats. then remove the original adjust your levels and then export it to a ready-to-use file.
(the last step might not be needed if the very start of the file is where it should be including empty space before the vocals come in.)