I've been looking for a good fixture to put over my 30" tank as well, and from what I've found, you're probably going to spend a little more than $200 unless you find a good used one.
Really it depends on what you want to keep. If you need high PAR for SPS and other light-intensive corals, I'd recommend getting a six bulb fixture. I have a 20g long tank which means it's shorter than yours, and I'd really like to have a six bulb fixture for it. Unfortunately, you're going to spend more for it. If you are wanting to keep less light sensitive corals, then a four bulb fixture would be just fine.
If you don't mind having the dark spots at the ends of the tank, a 24" fixture would be OK, but I'd really recommend finding a 30" fixture. Take a good look at Marine Depot and get some ideas. Their prices are pretty high, but you can usually find what you want and get it from a sponsor store at a better price.