Yea i was thinking about trying one of those canisters out too. I wonder why it took so long for a company to put a UV light in their canisters.
I have two Fx5's and a 30gal heavily planted sump, to filter my 180gal. Like everyone says...just depends on how heavily you stock it. Id start with a large sump...55gal...and one Fx5. That way if you need more filtration you can add Fx5's (which are easy to set up and a sump is not easy to set up). I say always over filter because, when you run across a supper rare fish a LFS, you want to know your tank can support an unplanned rad fish.