2x 250wt 10,000k Uhio's on a dual PFO ballast along with 2-4 "03" Actinic VHO's on icecap 660 ballast would be great lighting for your 75 gallon tank. If you wanted, you could also go with 2x 400wt 10,000k Ushio's (or any other bulb type you wish) on a PFO (HQI) Ballast along with some suplimental actinics, if you preffered more of a blue tank..
I think it would be best if you narrowed the choices down, for the fact that there's way too many possible ways to go with halides. I run 2x 400wt 10,000k on a dual PFO HQI ballast along with 2x 65wt "03" Actinic Power compacts over my 80 gallon. It really depends if you like a crisp white tank, bluish tank, yellow tank, etc.
Graham