Voodoo Lab

I have just acquired an Alesis Midiverb4 that i am adding to my amp set up. i currently have a Marshall Vintage Modern halfstack and want to also add in a Fender Twin. The questions i have are probably foolish but i am new in the rack world. Could i use the GCP as a AB box to control effects and which amp is being used?

The Ground Control Pro alone will not be able to route the audio signals, however with a GCX added you would be able to control the MIDIVerb and simultaneously select which amp is active and even control any switching functions on the amplifiers.

would i still need the GCX if i just wanted to control the midiverb 4 functions alone for now?

Only the Ground Control Pro would be needed to control any directly MIDI addressable devices.