Here is an article on some reflectors.
http://www.advancedaquarist.com/2009/1/review
I use both the LumenArc 3 and the LumenBright 3 in 4' wide tanks. I prefer the LumenArc 3 as the spread is better. If I was doing a 3' x 2' tank I would do a 400 se in a LumenArc 3 with a couple of T5HO or LED strips at 24" above tank.
The ReefBrite Hybrid looks interesting as well but I don't think you would get enough spread for a 36" long tank with a single one. I think 2 x 250w would work well in that tank but it depends on your budget and monthly power bill etc.
Cheers,
Tim