I was just talking to Jake (psykokid) about this...I am sure he'll weigh in sooner or later. He had a nano in his 60 standard and it was kicking up a decent wave, but he upgraded to the full wavebox and I inherited the nano (and found it worthless on the 24" tank). It got traded off, otherwise I would let you try it. Maybe someone else will step up.
I would think about going for the big guns, especially for the cost of even the small one. You will be more satisfied with the wave, 2" vs. 3/4", and the gyre it creates makes for some nice, broad, healthy water motion.
on a tank that big saba i'd reccomend going for the full sized wavebox. To get a decent wave on 5' tank you will have to run the nano wavebox at full power. Its at the very end of the acceptable range. I went from a nano to the full sized on my 4' 60 gallon and for the nano i had it running at 18V and the wavebox at full power. For the 6215 i'm running now i have it running at 12v and about 1/4 power and it makes the same sized wave as the nano did which is around 1" currently.
Also, on the nano wavebox it may or may not have enough internal volume to push out enough water to make the wave before it starts sucking air.. If someone would let you try out one before you make the plunge that would probably be best.. You can also ask roger in the tunze forum what he thinks as far as which would be a better fit. Hope this info helps.
thank you guys for all the info, if i could test one out that would be great but not counting on it. if it really isn't strong enough then i'll just have to hold off until i can save some more money, can't afford the full sized wavebox at the moment...