Listen to randy, you'll be fine with 175s. You could go with T5s for supp instead of VHOs.
As to T5 vs MH, I've done T5s a few times but without the ripple I don't feel like I'm under water.
this will be my 5th large reef tank that I've done since I started keeping mixed reef tanks. I've tried a few different light set ups and combos
had VHO lights over one of my smaller tanks and it was OK just OK..
right now over my 180 I have 3 250 MH with XM 10K's I thought I had ushios must have switched last change I guess 9 months ago.
the tank has a 1/2 glass canopy each side has a 8" brace and a 14" cenetr brace
so pretty much 1/2 the tank top is restricted light wise even though I wipe it clean daily it's still not 100% clear and I have amazing coral growth
I have a purple rim monti that is 18" wide 12" tall and growing out of the water.
my thinking is with the open top and the lumenarc's all of the light produced by the 175's will me directly in tank.
I kinda like the 10K supplemented with VHO actinics
my actinics are on 14 hours a day and MH 12
might drop the photo period down to 12 and 10 and see how that goes
looking for a around a 120 acrylic, but i need a 60'x18"x 20 or 24
Odd sizes like 60" tanks tend to be more expensive than tanks in 2 foot increments.
you simply have waste that you really cannot use. I'll have a couple of odd size pieces because I choose to make the width of the tank 36"
I could go 48" width but get into the lighting thing I'm trying to resolve.
a buddy of mine has a 36X36X30 cube and he has one single 175 MH over it with a lumenarc and his tank is doing real well, his corals are well placed and tank looks great