Are Icecaps superior? That's a tough one. They certainly don't have enough track record for a solid reputation for reliability.
Those of you who have had the first VHO ballast (or read the articles in www.thekrib.com)
should recall the problems with the first generation VHO ballasts (early 90's). Their MH ballasts are NEW and, like car buying, I prefer to wait till they work out all the bugs.
Based on the current articles and manufacturer's claims the Icecap ballasts appear to be superior. But as I said earlier there is no independent study or test performed on them (that I know of anyway). The few articles I read on the internet are written by people in the hobby that may or may not receive personal gain by giving Icecap a good review. We should rely on our peers here for honest comments on this product.
I wonder if Icecap will ever build a 400 and 1000W ballast. The hydroponic industry would like to see a cool and efficient ballast. And knowing how these "plant" growers spend their "easy" money, Icecap ballasts should become their preferred equipment.
I better answer your question about sourcing MH bulbs. Philips, GE and Osram don't market any 175W MH with more than 4300K that lighting wholesalers would carry. They may manufacture aquarium bulbs with a different brand name though. Iwasaki don't make any 175W bulbs at all. So you are stuck with costly aquarium brands.
I think the 175W format is limiting your options. 400W bulbs with >5000K colour are readily available from many manufacturers and in turn are available from your commercial lighting warehouse. Their prices are more competitive but the cost of electricity is obviously higher than a 175W.
What do you need? How big/deep is your tank?