to the floor? the amp. manual said that installing the amp on the sub. box may damage the amp.but i see many amps.installed on the sub.box and they had no troubles i do not want to take any chances.
Usually the reason for the manual saying that is because many people neglect to secure their boxes. In doing so the boxes in turn can fall over or slide around and damage the wires going into the amp or possibly the amp itself.
It is perfectly fine to mount your amp to the box just make sure the box is not going to move around and damage the amp at all and also be sure there is enough air space around the amp to ensure it doesn't over heat.