I've been quite pleased with my setup. PSR9000, Mackie 1202VLZ mixer, 2 JBL EON powered 15's. Since JBL has some EON 2's out now, the older ones are quite inexpensive compared to the Mackies (about half, in fact), and are somewhat lighter in weight. I think a really good system, although a little heavier in weight, would be JBL powered subs, and 2 powered 10-inch speakers, but I've never actually heard that setup.
I have another setup that consists of a Peavey 1000-watt digital power amp (10 pounds), rack-mount Peavey Deltafex twin for digital effects, Alesis stereo graphic e.q., and 2 Peavey 115 speakers. The speakers are quite inexpensive and sound really good. They weigh 29 pounds each. If I am in a situation that requires monitors, I plug two Hotspots into the back of the mains. The heaviest part of the whole rig was the rack case, so I made one myself out of a Coleman ice chest!
I even printed a sign which says "Red-neck Road Rack".