yes , true I have one client that have buy 3 Roland PCR-800. The MS is used on bottom as master keyboard with the all sound system. 1 PCR-800 Jack connect to the B4 ASIO host as second manual. 1 PCR-800 Jack connect to ASIO Host 1= Superwave P8 1 PCR-800 Jack connect to ASIO Host 4= NI Massive.
In realtime you can continue use the full features of the MS OS as a Master system, but PLUS the other 3 PCR controller for always play realtime the others engines!
This is the Open System, you buy only 1 keyboard and you wil use like you have 4 keybsoards! Each PCR-800 is like a embedded Synth. Is really fun, simple to use/connection ( only 1 USB cable) and at the end COST less!