My old band used to have a couple of JBL mains with 2x15" speakers plus horn. They took up pretty much space during transport, they were not the easiest ones to carry, and mostly a smaller setup would have been enough. We also had four 15" and two 18" subs (we never brought all of them to a gig though). All speakers were passive, so we had a couple of mackie power amps with built-in high/low pass filters to feed the speakers. They were really good.
If I would buy a PA today, I'd go for an active system with 1x15" + horn main speakers (300-500 W each) and two 15" subs (500-1000 W each). You might get away with less money if you go for a passive system though. I would not recommend to go for only mains without subs, you do need the extra bottom they provide. That's what brings the chicks to the dancefloor...
