Craig,
I know you can do this with the S90ES (because as you stated it does have the Motif soundset).

You can do it to some degree with the T2 as well--but that's really just because (IMO) of the optional hard drive which would let you load in new samples.

I think a Korg or Roland high end arranger would favor better for (out of the box) Hip Hop though. That's because (IMO) Korg and Roland do a better job at "synth" sounds, and (IMO) I think you get better voice editing options with a Korg or Roland.

Squeak
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GEAR: Yamaha MOXF-6, Casio MZX-500, Roland Juno-Di, M-Audio Venom, Roland RS-70, Yamaha PSR S700, M-Audio Axiom Pro-61 (Midi Controller). SOFTWARE: Mixcraft-7, PowerTracks Pro Audio 2013, Beat Thang Virtual, Dimension Le.