Ive being looking into this myself recently and have come to the conclusion, you are going to need two samplers. You need two because one has to load up while the other is playing and vice-versa. Its the way Orbital work except they have 4 EMU 4xt's
also i would go for an EMU or a yamaha because they have more real time control,and better MIDI for playing live.
Also i would use a computer based sequencer