After owning a line of cheapos I got a turboflotor 1000 and made about 10,000 adjustments to it. It works well, after the adjustments, but I would look to spend the most on your skimmer until you get into the difficult corals, then its your lights.
Skimmers and RO/DI units have made my tank operational (until my wife springs for a Deltec or bubblemaster)