Light Question,2 400W or 1 400W 2x4x7

Well I am using a CMH 400W, and I was debating getting the 30 inch cool tube to fit both in, but I am only working with a 2x4x7 room, my question is, how much % yield gain could I expect on my grow? If the finished bud amount would be dramatic, I guess I will go ahead and buy this cool tube, and a more powerful 6inch Exhaust fan.

I would be replacing a side mounted 8 Bulb T5 fixture with 4/4 veg/flower bulbs(Lop sided side lighting at the moment), and the CMH I have actually runs cooler than the T5's, and is only 48 watts less!

What do yall think?

Heat should not be an issue.

Nevermind, I just found out that It will be 8,000 Lumens per sq ft with two, and half that with one, since the sun is 10,000 I guess it literally would produce twice as much.

Thanks for those of you that at least viewed this thread, sorry for the repeat question!