i use redrum mostly for kicks and snares, sometimes hats.
i use the dr.rex to layer breaks ive chopped up in recycle.
i should get around to using nn-xt with a break, find a nice hit in the break, copy and paste zones, pitch up pitch down - that way u can use the same hit but cos the pitch difference it sounds more natural, something that u cant do in dr rex, unless u load multiple rexes with the same break in...
and as far as scream goes with percussion, tube/tape for the win for a sharp metallic snare sound
met a dubstep producer the other day who said he never uses scream, only the foldback distortion unit. i had never seriously used it until he said that, now getting some sounds out of it i havnt been able to from scream - altho cant say i even understand what foldback distortion is!