72gal bow front lighting and power head question

[rayyue]

i just got a new 72 gal bow front for my new mix reef tank
want to put some sps on top and lps and sofe coral in the mid and lower area.

now i got two k4(1200gph) and three k2(600gph)
my question is i should use two k4 total 2400gph (33.33x)
or use three k2 total 1800gph (25x)

and the tank is 21" or 22" tall
now i got one 150w mh
i should buy one more 150w is enough
or buy a dual 250w mh

and the return is 300gph (4x) is enough?

thanks