you may have overlooked a USED fixture at a local fish club or ebay. retro kits are for custom canopies or custom pendants. you will need more light such as PC's for supplemental lighting because the MH's will only be on for a portion of the day. IMHO i think if you have the money then the fixture is the way to go, this is my opinion and not a rule though. maybe someone with Halides can be of more help, but i hope this gets you going in the right direction.