Couldn't say, but the M5 is cool.
Anything for a Benelli M2/M4
No, it's soft as heck as it is.
A400 Lite Synthetic bbl, but you need the spacer as well as the bbl. Any 3" A400 fire control. Stock and F/E from A400, etc.
Absolutely not worth it. Aridus stock adapter and it's already shorter than the SBS M2 as Tim mentioned.