Picked up my new M3W today, and by the sound of it I am getting the same banging noise on hard acceleration (plus the sort of Bevel Box whine that I thought MMC had eliminated a while ago). I will have to look at the cost of securing the Box to the chassis as suggested above.
Otherwise, it's fantastic.
Welcome to the M3W fold

Is it a Euro 4 spec??
It maybe stating the obvious but if it's a new car I'd talk to your dealer about the banging.
Re the bevel box noise it's unlikely MMC would take any notice until you have at leat 1,000 miles on the box and it mightend up being comething you can live with.