Complete overkill, but I find Ableton Live to be the best app for timestretching, pitchshifting and re-syncing a loop before chopping it up. Just load your samples into the grid, get them sounding how you want them, then render them into new files, simple and fast, but not cheap at a 500 dollar price tag. I don't even use it as a sequencer anymore just as an editor for loops for a couple of esoteric functions a regular editor can't do with ease.
DSP-Quattro is a great 2 track editor for OSX, does just about everything that Peak (even SCSI transfer to your s5000

) does and is written by the same guy that wrote Spark-XL for TC. It runs for 150.00 and is a no brainer for a 2 track editor on OSX IMHO.
I played around with Audacity but found it a bit annoying to work with, but I'm not one to complain about free.
-d