Placement of amps ?

You can place your amp wherever you want, just be sure it's on a hard surface so it has good ventilation.

Wherever the amps are placed, it is most important to isolate them to a high degree. This is true of all components in your listening room. The room, set up, placement and component isolation are all critical components in getting the most from your system. This could be the difference between sounding like good hi fi vs a magical system.

A large amp on the floor in front of the speaker could affect imaging/soundstaging. Reflections from the floor in front of a speaker are the first reflections of sound waves that you hear. That's why it's good to have a carpet in front of speakers to absorb some of the reflected sound from that point.