I've seen people use 175's on tanks larger than 75gals, but IMO
I would use 250's. This way you'll have plenty of light even towards the bottom of the tank. Also if you get a larger tank later on you would still be able to use the 250's. FWIW
, I am very happy I went w/ 250's on my 55gal. SPS
's color up and grow very nicely for me and I'm able to keep a Crocea clam happy on the sand bed.