I use the Marineland Reef Capable LEDs over my 29g.
They are sufficient in my 18" deep tank. That's about it -- sufficient.
I highly doubt I could keep anything more interesting without upgrading my lighting....and I plan to upgrade when I can.
I am thinking of going with the chinese 3watt LED light over my tank next to see how it goes. It's only like $189.
You could get two for your 4 ft. tank i think. It might be over your budget, though, and I am taking a chance on them...I don't know for sure they will be any good. We will see when I get them. haha