underworld used Akai MPC 2000's on stage for midi sequencing. (with sounds coming from other Akai samplers, maybe S6000). Not sure about the black box, although it might be a custom built piece of kit that triggers certain sequences so Rick can easily do those 909 drumfills on the fly.
Along with the MPC range (of which there are also newer, smaller models released in recent years) you might want to check out Yamaha RM1X or EMU command stations which are groovebox style machines that also have their own inbuilt sounds (but you can use them for sequencing external instruments as well). For analog step-sequencing check out the Doepfer MAQ 16/3
Orbital famously used Alesis MMT8 midi sequencers for their live shows.
RM1X's especially can be found for cheap 2nd hand (maybe 200 euro) and are supposedly quite good live sequencers.
I have no personal experience with any of these, just telling what I've heard and read about
