Im with you on the moonlight I just have 2 white leds driven way low in my current tank that I really like. Rapidled has a 350ma moonlight driver. Have you looked at stevesleds, he has some cheaper drivers that I think are dimmable.
That seems like a more reasonable amount of leds, plus that will leave you lots left over for a real nice controller. However actually that only gives you 14 LEDs. You can get more on that meanwell driver so I would throw a couple more in. I think 20 or 2 rows of 10 LEDs spaced 3 inches apart with 5 inches between the rows would give you a good even spread.
Maybe this kit instead of the 6 led one, that would give you 20. since the drivers will run them you might as well, I believe in a little overkill, plus they are dimmable so you can pull them back. Just not 50 LEDs thats just crazy talk.