id say. get a 4 channel amp for the four speakers. and get another mono amp + sub (in sealed enclosure). would satisfy your needs easy.
for the sub, id recommend jbl gt5-12. should cost around 7k.
sealed enclosure of 1.4x1.5x1.4 dimensions in mtf should cost 2-3k. soend rest on two amps. try to get branded amps even if youve to add a couple of more thousand ruppees.
and get the system tuned by a proper tech. youll love the sound.