700W?

Thats pretty hefty mate. If you want something decent expect to pay around a pound a watt

These would be a good investment:
http://www.decks.co.uk/products/spea...ckie/srm450_v2

The resale value would be very high, but you could probably pick some up second hand as well. Much better off going with a good brand 2nd hand than something budget and new.

Avoid all the cheapy PA types - they sound shit and don't last. If you want 700W you need to pay a decent whack to get a decent speaker.

Buy something decent, and you'll make your money back when you sell them. You can also rent the powered ones out really easily - just plug in and play. Dead simple.