I'm with Gresham, you need a powerhead to ramp up quickly and push a lot of water fast, streams are designed for this. That's not to say that a modded maxi might not work, just as the size of the box/tank volume gets larger the size starts to matter more.
Saw this on Youtube, DIY wavebox with a 6000 Stream (is this a controllable model?) But seems fairly straight forward. You have... a box... instead you have a pump. Don't see why this couldn't be an external jobber.
http://www.youtube.com/watch?v=W1duSSdjRb4
However if you don't care about the standing wave, I think you can very easily get away cheaper components, the two main ideas is you drain a ton of water from the external box into the tank (via pump) very similar to a surge (if you have a 10g surge that dumps in 15 seconds, that's the equiv of 2400 gph which is where Streams pop into the picture). Then you get the pump to shut off, and the reverse will happen as water rushes back in (most likely not the same amount simply because the tank does need to fill back up from your return pump as your overflow will get swamped). So you get a series of two surges per pump cycle. Who needs a standing wave!
If it were me, I'd find a really junky acrylic tank, and just build a smaller version as a proof of concept to see how it'll work, realizing as you scale up things change drastically (also when you add silly things like rock & corals
)