Nathan is right... With the Bio Cube you can keep low light corals. If you want to keep anything more than low light corals, you are better off just buying a bigger tank. You'll be able to keep a lot more in it.
I'd be hesitant to recommend to someone to spend a lot of money right off the bat. If you enjoy having your Bio Cube over time, then it will be much easier to make the decision to spend more money on better lights.