How Many Mitras?

[asylumdown]

Hey folks, I've been considering upgrading my lights, presently on a 6'x3'x27" tank I have 8 radion Gen1s with the TIR lenses. I probably only needed 6 lighs, but at the time I was planning this, I didn't trust LEDs that much, and wanted to have too much light as opposed to too little. As a result, I can't run my lights any higher than 75% max intensity.

How many Mitras's would I need to cover the same space, and still be able to grow SPS on the sand-bed (which is about 25" down)