Get a another powerhead. I don't know what gallons per hour a mag350 shifts, but you'll invariably need more than it provides. Look for a total of at least 10 *tank volume shifted per hour, and even that doesn't look like much.
Have you done your homework yet? I don't want to lecture, but reading first is cheaper than killing a few hundred dollars worth of stuff and then reading. If you aren't sure you need a protein skimmer (you do!) then 25 dollars on Mike Palettas New Marine aquarium will save you some money and heartache.
Decide on lighting when you've decided what you want to keep. Fish only, normal fluorescents will be ok, but for photosynthetic inverts (corals, anemones), you will need metal halide (expensive) for a tank this deep.
Research, research, research. Your tank is a strange shape. What this means when it comes to fish is that a lot of fish that people say are 'good for 55 gallons' will be too big for your tank as the swimming lengh is not there. Tough luck on that, though I be it looks good.
I'm setting up a 30 at the moment that has a similar 'footprint' to your tank. Red my thread at the top, and take note I'll spend at least 6 or 7 weeks fishless before anything goes in as I would like to have a low maintenance, low hassle experience!
Good luck!