FWIW, a lot of the products we pay a premium for under an aquarium brand, are really common products available in other places. PFO and Hamilton (as well as many other's) use Advanced Ballasts (Grainger, Home Depot, etc.), a SeaSwirl is nothing more than some PVC that's been routed, a job-box from Radio Shack, and a stepper motor (grainger...). "Alk Booster"? Arm&Hammer.
Lighting in particular, is one area a lot of folks have gotten by spending far less, by being creative. HOWEVER... I've met a lot of folks trying to dump Mercury Vapor ballasts they thought were cheap-o MH ballasts from HD. Buyer beware. Much like my opinion on computers, if you really don't know what you're doing, don't even bother cracking that case open. You're just asking for trouble. If however you're comfortable w/ the risks, know what you're doing and don't mind getting your hands dirty from time to time, you can save a TON of money over buying everything at an aquarium retailer. I just advise everyone to be very cautious, as minor differences can have a large impact.
- Mac