If you are going to place the Atom inside a built in cabinet - then I do not
reccomend it, due to the rear firing port - this can change the character of
the bass response, and can cause it to sound boomy, and lead to a muddy
sound character. Need to know the room size, to confirm the size of the sub.
The Marantz 6006 has good power, I would not worry about needing an amp.