They have decent surface area, but I'm thinking its gonna be hard to build a decent aquascape. In a 6ft tank with reef, and even just for the fish, building aquascapes that provide swim thru areas and spots to place future coral and small rock (it'll be attached to). I'd probably consider using a decent amount of base rock that you can build with. With the live rock you've got established already in the 55g, you can easily seed the base rock. Cheaper too.
"Life may not be the party we hoped for but while we are here we might as well dance!"