Thanks for providing those numbers!
Yea, Mh + T5 is always a solid choice. BTW, you can do the cool sunrise and sunset effects with T5s. If you get a dimmable T5 ballast, you can just dim it the same way that we dim LEDs, with a 0-10v dimmer channel in a controller. Also, you said T8, I said T5. I guess you could do T8, but I'm not sure that there are broadly available T8s for reefing. I'm only familiar with T5s and VHOs which I thought were T12?
With the 180 you can't go wrong with 250w x 3 + 4 72" T5s, two on each side. Just make sure to get nice reflectors for your 250w, and you're golden.
If I did a 6' tank though, I'd probably try out a 400w or 10k XM on a moving light rail and just T5s/LEDs the entire length. There is some good evidence that you'll hit photosaturation and still get great MH coloration with a setup like this. Might be worth looking into.