Decent sound in a disco is totally achievable.
I have a Sony headunit (40w x 4 channel) running the original tweaters, 150w 2 way 5" door speakers (in the usual holes) and 200w 6x9's in the rear pillars (where the original speakers were)
It still lacked any bass sound so i fitted a 500w amp, driving a 300w 12" sub woofer which live's in the boot.
All together it sounds absolutly super'b!!
Plenty of bass, mid and top sound which suits whatever style of music i feel like listening too
:D