I would get an M&P40 and an SR9 instead.
You can buy a factory M&P9 barrel and drop it in the M&P40 with nothing else to change.
EDIT: I guess I should clarify...
Instead of an SR40 and M&P9, I would get an SR9 and M&P40, for the reason mentioned up there^.
This post was edited on 11/21 at 7:45 pm