Amp control depends on the amp.
HXS/HXSXL both transmit MIDI PC, CC (single and toggle) and NOTE.
You may run into difficulty depending upon what you need to transmit and when.
A FS can only send a single MIDI message.
A Snapshot can send more than one, but if for instance, you need to TOGGLE CCs, you'd need TWO Snapshots for that, and since you have only 3 (HXS) or 4 (HXSXL) that could limit your options. Also, HXS/HXSXL do not have simple amp control (channel switching). So, unless your amp uses MIDI for that, that would also limit your options unless you get a MIDI switching device like the VooDoo Labs Control.