Need some ideas for lighting a five foot tank...

[hlywd]

So after a year of using a 54g corner tank with a canister filter I acquired in 'used' status I'm finally in the process of upgrading. Everyone told me how cheap, easy, and forgettable this hobby is, and I've fallen hook, line and sinker for it (no pun intended). At any rate, I'm really looking to upgrade into a 150 to 180 gallon tank, and there's a perfect spot in my house. The only issue being, it would fit 6' but I think a 5' would look ALOT nicer. The main thing I'm worried about is the lighting. To build a 180, the tank would have to be about 28" deep being 5 feet across. After talking to a couple lfs they both quickly told me that a four foot light would work. So here's my question(s)-will a four foot light work on a five foot tank being 28" deep? Also, what would you recommend for lighting in this tank (I'm leaning toward some type of mh 250)? Also, if anyone has any applicable lights for sale, I'd be interested in hearing about them. Thanks for your time, and I look forward to hearing from you.