Following on from my last post, I recently bought AutoSampler from Redmatica, and I have to say, it is absolutely brilliant! Can't fault it for results. So far I've made loads of multi-sampled, multi-velocity patches of my synths (2 or 3 at a time for a huge sound - e.g. Wavestation, matrix-1000, JX-10) and AutoSampler has done perfect loops time, after time for Kontakt, Reason and Logic's EXS-24.
If you want to make samples of your rig, I highly recommend that you try this piece of software out.