I've got an AquaGlobe AQ-200# in my 7G nano + the penquin HOB pushing a little more and quite frankly I think I could use another 100-200GPH.
The AquaGlobe is smaller than the mini-jet and they have a 100GPH, 200GPH, and 300GPH model. Not sure of what stores carry them but Dave ESPI on nano-reefs.com sells them. They're awesome other than the fact the suction cups are wayyyyy too weak and the thing will fall all the time if you don't change them.
I use two maxi-jet 1200s on my 6 gallon eclipse. Instead of worrying about their size, I just plumbed them externally. I don't think I get too much flow at all. I think that it all depends on exactly what you want to keep in your nano. If it were me, I would tend to error on the big side. You could always point the powerhead at the glass if it were too much flow.
I have a 1200 and (I think) a 600 in my 6 as well. They're 295 and 160 gph. The old rule of thumb 20X tank volume doesn't work so good in a nano. It's all about velocity, not just total flow, and the little PHs just don't cut it. I had the 400 in there and it hardly pushed the water around. It all depends on what you're keeping of course. I have SPS corals so I need a ton of water movement.
I have a rio 600 in my 7 gallon. An important thing to remember is to have maximum water flow but not current (intensity). It is better to have your water flow more evenly distributed. So I guess what I'm trying to say is..... Move your tanks volume as much and as gently as you can. Trust me my corals would tell how happy they are if they could.
I have two Minijet 606s and am happy with them after upgrading from 404s. They are nicely adjustable and easy to maintain. I have a 10 gallon also FYI...
I use only one Minijet 606 in my 10 gal. nano. And I use the middle setting since I only have Pocillopora, mushrooms and giant Aiptasia, peppermints and an emerald crab. I recommend gluing an algae magnet to the powerhead w/ 5 minute gel epoxy. Twister magnets work well. The epoxy hardens in an hour and is ready to put in the tank.