Most inexpensive "wavemakers" don't really make waves. They alternate power to 2 or more powerheads. That gives some variety to the waterflow but I believe in general that you can do better. If those powerheads are each on half the time then you're only getting half of your potential flow from them.
Powerheads (with or without wavemaker) are an inexpensive way to increase flow within a tank. They are not the most efficient way, though. Minimum flow rates for your tank should be about 900 gallons per hour. Your sump return pump will provide some of that...Maxijet 900s deliver about 230 GPH each. So for a minimum flow configuration, 3 could be enough. (Of course, if they were on a wavemaker power strip, you'd need double that.)
If you eventually decide that you want to keep corals that need high flow you'll want 4 or 5 times that amount (~ 4000 gph) It takes a lot of powerheads to achieve that (8 to 10 maxijet 900s!) The electricity for those powerheads would be much more than an external pump of the same total flow rate. Plus powerheads transfer relatively large amounts of heat to the water. Plus, they take up space in the tank (and don't look particularly great...) Finally, they blow their discharge in one particular direction (hence the use of wavemakers) but that type of flow ("laminar" flow) isn't the best for corals...the ideal flow paterns should be random and turbulent. The best way to achieve that is to have the water streams directed at each other so that they don't blow directly onto corals. (This configuration is hard with powerheads since you probably wouldn't want them in the front or sides of the tank.)
The alternative to powerheads for getting very high flow rates would be a closed loop...an external pump that takes water from the tank and pushes it back into the tank ("closed" meaning the circuit is never open to the atmosphere as a sump would be). Many of the best RC threads on the topic can be found in the All Things Salty forum...look for a couple of sticky threads at the top of the forum regarding closed loops and manifolds. Using the "Calfo" manifold allows you to distribute the return flow to avoid laminar flow patterns.
This is not intended to tell you that you must do a closed loop. Just letting you know where you might eventually want to go. For maintaining a budget (as if this hobby could ever be affordable...) powerheads are an attractive way to start out as long as you are content to keep only corals that don't have requirements for high flow rates. That really does leave you a lot of choices, especially as you are getting started.
