I use the AB's - 800 and 1600. Do ok for what I need. Just keep in mind those numbers are misleading as they are only actually 320 and 640 Watts.
I've hired an Elinchrom Ranger RX kit before for which I used in bright sunlight (this shoot:
BMW 1M Coupe — Jan Glovac Photography) and they were brilliant. Pricey though!