Let me get this straight: you have reflectors (and thus presumably sockets) coming, but no ballasts? Sounds like a perfect match!!
What depth of tank are you using them over? I've used 175's over several different tanks, most recently a 90g with 24" depth. It was just sort of on the threshold for my 90g, some things liked it, but some things seemed to prefer more. I had 4 clams in there and they were fine, for example, but I found I needed to keep my SPS higher up or they'd tend to brown out. I did have the lights fairly high (8", I would have preferred less actually, but I didn't have the canopy for that). When these lights were over my 72 and when they were over my 55, I had really good results with just about everything.