I've used Marine Depot, premium Aquatics, hello lights, Aquarium specialty, and others all with really no issues. I have never heard of the company you linked. Generally I try to buy from RDO sponsors.
Used them once a long time ago, they used to have will call (local place) but not any more, nice support as I mentioned a bulb wasn't working and all the while cursing them out because they didn't reply... in the mail came a new bulb.
I think you can retro something close at PA cheaper,
IceCap 175 watt Electronic Halide Ballast $119.95
Mogule Halide socket and bracket $9.95
RF PARABOLIC REFLECTOR ONLY $23.95
Total: $153.85
Hello lights has retros, using ARO electronic ballast for $130.