The more you know/understand the better off you’ll be @Bogleg, so feel free to ask away. As far as planning for next summer, the latest and greatest will probably change at least twice by then. So don’t start buying little pieces of the puzzle now. Your best bet will be to stash a few extra bucks here and there when you can until you’re ready.
Right now quantam boards, and citizen cobs are the hot topic on diy end. The hlg-550 retail $1050 currently has coupon code for 20% off, and diy build would run you around $600. They are getting ready to introduce new light, hence the sale. But that’s the typical margins you’re looking at with diy. For reference, you could pretty much do anything you damn well pleased in a 4x4 with a light like that. It should provide plenty of coverage wall to wall. 2 plants now, scrog in half with a couple of plants on other side, or whatever. You’d be good, and hassle free at a little over $800 wouldn’t be bad. If you’re a tight ass and don’t mind a little elbow grease, you could save $250 and build it when components are available.
If you’re more budget minded, building something like 200 watt cob bars is a pretty good option. You can usually get into a pretty good setup for about $1/watt give or take. If you want to give up a little efficiency to save on build cost, probably even a little cheaper. But that would give you the ability to build a bar or 2 and grow your 2 plants, an add another bar if you decided to go back to something like a full tent. Or even just build the one fixture into a square and deal with any shortcomings until you have a little extra cash. Then reconfigure the same cobs later if you decide to go a different route.
You’re only really limited by your budget, and how creative you want to get.