How big are you looking to go? A 40 breeder can make a good basic frag tank. Or you can go with a shallow tank that will give you lots of room. If you want to go really big, there are those shallow tubs that all of the adicts use. lol!
40 breeder is a good choice. Also try glass cages, or deep blue. One of our vendors on here is Reef Savvy, they make awesome tanks. I'm sure you could get a custom tank from them too.