The MPC1000 with JJOS2XL kicks ass for sequencing hardware. I used to run all my synths off it. Never used the RS7000 but many here swear by it. Probably either one is a bit of overkill to run just 3 boxes but will be able to handle more synths as your collection grows so you'll never really need to upgrade. Both options add sampling as well but you might find the MPC is a bit more user friendly in that area and also will have a lot more 'ready to play' sample packs available, not to mention support network, user base etc. is bigger.