Yes, it's the lower right board, rev. 2.x with one chip.
The 4-slot expansion board can hold multiple expansion cards. Sometimes board like the M4 are build with the connector you see on your picture. Often a cable is included to connect the board to either a Schneider 6128 or Amstrad 6128. Both are the same computers, but the ports are different. The Schneider has Centronic type ports while the Amstrad has edge connectors.
I will make the pricing as soon as I ordered the PCB's and checked the pricing for all the parts.