I got mine at Premium aquatics. If you're going for maximum PAR, I'd consider an XM10K in a lumenarc overdriven with a 400W "HQI" ballast...it's in quotes because I've heard from a fairly reliable source that the ballasts sold in this hobby as 400W HQI are not actual HQI ballasts, but they mimick the effect that HQI ballasts have on bulbs. The guy that makes the lumenarcs is not a fan of these ballasts; he claims the good old M59 is the best for the bulbs. Lots of people love the reeflux bulbs.

Regarding the coverage, the lummenarc's claim to fame is that it focuses the light over a very clean square pattern. Since your tank is like 2 squares next to each other, if you want perfect even light distribution across your whole tank, your best bet is two lumenarcs. If you do that, you could get the smaller "mini" lumenarcs which would give you room for some T5 actinics, and you could easily bump down to 250W which would allow you to get the true HQI ballast, or even just M58, and have PLENTY of light.

There, I just spent several hundred $ of your money.....sorry!!!