Personally... and just my opinion as I've never dabbled with them... but I think most the wavemakers out there are overrated. I mean, they're just timers that cycle your powerheads on and off. It's not the random/chaotic flow pattern you really want, it's just not constant. Seems like it'd still be a cyclical pattern, and a pattern is a pattern. The surge-type wavemakers seems like they might make more sense, but for small tanks they just take up too much room.
Personally, with a 37g, I'd just go with a couple powerheads with some creative "bank shots" of rocks or glass to get a somewhat chaotic flow pattern. I started out with MaxiJets in my 46g and liked them, but have since switched them out. The Hydor Koralias really give a lot bigger flow "cone" and it seems to make it easier to make a more chaotic pattern. Don't let the high flow rates on the Koralias fool you - the #2 at 600 gph
in reality is more like a MaxiJet 900 at 230 gph
... it's just a wider flow pattern.
But... if you're going with a wavemaker, I'd suggest 3 powerheads I suppose since they all won't be on at the same time. That's probably the right amount. Maybe 3x MaxiJet 900s? You can always start without a wavemaker and then add it later if you feel you need it. With or without a wavemaker, you're going to move your powerheads around 4 or 5 five times before you find the "right" combination. And then after you start adding corals, you start moving them again!
But I really like the Koralias!