Lighting a 120 48x24x24 help?

[XSiVE]

I'm seriously considering switching from my 2x250W Halides + 2x54W T5's to LEDs on my 120g reef. I keep SPS and LPS with a few other random things.

I was thinking that 4 rows of 20 LEDs would work okay... mixing cree XRE Q5 and XRE RB with 60 degree optics..

It seems like Mike got a ton more PAR than what Im looking for with his setup at a similar density, but with 40 degree optics, but using a dimmable driver I could probably dial them in to where Im looking for.

Am I on the right track?

also, Im not really sure about drivers.. I guess I should take a quick refresher course in electronics