There's a piece in the Global article (within another thread in this section), where either Mark or Tom state that (at that time), all they really needed was a sampler and a good FX unit !
I think this pretty much sum's things up.
Off course, those two, and a bundle of ideas as well.
I know the sound you're looking for, Guest, and as Mr. Chuck also states, the purest way to attain it, is by trial and error.
If I was yourself, I'd try to look into samplers (if you haven't already), and get your head around them. Reason has the NNXT, which (to my understanding), is da'bomb !
There's also Kontakt out there too by Native Instruments, and a host of others, and a HUGE host of FX applications too.
I'd try to start with a good idea, and then with the sleeves rolled right-up, get tore into the NNXT and Reason's FX.