I've had the chance to work with Arri's 650 and 1000 watt lighting kits a few times and they are beautiful. The fresnels allow the lights to be adjusted in Flood or Spot which makes them easier to throw the light where you need it. Of course, they are a bit pricey. Just a few months ago I posted an article about certain lighting kits that claimed to be 'As Arri' found here: http://cheesycam.com/arri-blueline-jietu-fresnel-lighting/
These 'As Arri' lighting kits sold at less than a third the price and claimed to be an exact 1:1 replica of Arri lighting kits. So close in fact many of the replacement parts can be ordered from Arri such as the bulbs, Fresnel glass lens, ballast, barn doors, scrims, etc. They are available in 150, 300, 500, 650, 1000, and 2000 watts. The most common kit being a 3 pc 650w should cover most situations.
Not much information is available on the web, so these still aren't very popular, but just recently a brave soul (Vimeo Member) Josh Donnelly took a chance and posted a video review. Looks like it's time to bump this one back up on the wish list.... [Thanks Josh]