can i put a filter stage after a large variable amp?

My senior design project is a simulated surround amplifier. It will take line-level stereo inputs and break it up into FR, FL, RR, RL, C, S. I would like to add the delay for the rear speakers and do the filtering for the center and sub after the the left and right channels have been amplified (this is an attempt to use two amps (left and right) instead of needing four amps-one left, one right, one sub, and one center).

_______master volume
|
__|__
| |----------------------------left front speaker
line | |
lev--|amp|-----delay---Vol control----left back speaker
left | |
| | _____
|____ |------| |----LPF---vol control--sub
|mixer|
amplified right--|_____|----BPF---vol control--center


can I do this and still get good, somewhat loud sound?

-juanicus