As a bit of a 'get to know your sampler' session, I thought 'OK, I'll mash up the Amen break, for old-times sake'... and I confused myself

So I dragged a WAV of the break into 5 different keygroups (one for kick, snare, ghost snare, ride, and the 'doosh' sound).
Then, I extracted the kick from the whole break in keygroup 1, and that went fine. But... then, all the bleedin' keygroups were cropped to just the kick sound!
Basically, I think I'm missing something pretty fundamental here - it's probably because (a) I only skimmed the manual today, though I've read it before thoroughly and it still didn't make sense, and (b) I am a complete novice to the whole hardware sampler paradigm that CW/SC have adopted for their samplers...
In an ideal world, I'd like to do all my topping and tailing of samples in the STS sampler, leaving the original WAV files intact. Is this possible?
Also, would it be worth acquainting myself with an Akai sampler, just so I know how the fuck these things are supposed to work? (I've got a mate with an S3000 that's literally propping his door open, and he said he'd be happy for me to nab it).
Help please? Thankyou muchly!
Chris