I can get the following amplifier, subwoofer and 6 x 9's. Which will be the loudest and best quality together.
Amplifier:
Powerbass PB4.140
Phoenix Gold Z500.4
Polk Audio PA660
Subwoofer:
Polk Audio DB1240D
PowerBass PSW330D4
Kicker CompD12
6 x 9:
Kicker CS6934
Polk Audio DB691