I think that 2 250w HQI lamps plus the two 96w actinic bulbs is gonna be a bit much over a 13" tank. Plus any all-in-one light like this isn't easy to re-wire a new ballast to. It's not the same as wiring up retrofits. If you're gonna buy one of these lights, (and I think they're neat fixtures), get it, put it over your tank, and leave it alone. Don't try to re-engineer it.
Personally I wouldn't spend $600+ on this fixture, then void the warranty by trying to upgrade it. You'd spend at least another $200 on ballast and bulbs.
So you've paid over $800, and now it's not under warranty, so you're screwed if something goes wrong with it.
You can easily spend the same $650 or so and get a retro kit that has 2 250w MH lamps, ballasts, and either 2 VHO or 2 PC actinic bulbs. You can go a bit cheaper and get 175W MH. All the parts go together properly, it's more modular for replacement/repair purposes, it's easier to sell if you want to change it in the future. Etc...Etc...Etc...
Check out
www.championlighting.com
www.reefgeek.com
www.hellolights.com
I've dealt with all of these folks to a limited extent. I've been happy with all of them. If you are not able to put together EXACTLY the light combo you're looking for, call them. They'll help you out.
B