Ive been thinking about this a bit and your best bang/buck would probably to get two of these drivers HLG-185H-C1050 and run 3 of these cobs off each one, CLU048-1812C4-303H5K2. You would leave 34v on the table that you could potentially use to run another 36v cob either now or down the road. You can get 2 of the 185's for almost the same price as a 320 and that would give you some redundancy in case a supply failed, youd still have some light... You could spend an extra $40 and get 1818 cobs and get a bit better efficiency, depending on your budget. I like the citizen cobs better than cree right now, even if they were the same price, but because they arent, it makes the deal even sweeter. If you really want to go with less cobs, like 4 total, Id do this
Prices are from CDI
4 CLU048-1818C4-303H5K2 @ 22.60 each = $90.4
1 HLG-320H-C1400 @ $93.20
4 MODULED MEGA 134100-B @ $19.63 = $78.52
4 ideal holder 50-2204CT@ $8
Total = $ 270ish USD
Nice thing about this is you can hang each cob/heatsink individually so they would be adjustable depending on the plant size nearest them. You can spend a little more and get better efficiency by going up to the clu058 series citizen cobs, which would work with the same heatsinks, just need different holders.
Prices are from CDI
4 CLU048-1818C4-303H5K2 @ 22.60 each = $90.4
1 HLG-320H-C1400 @ $93.20
4 MODULED MEGA 134100-B @ $19.63 = $78.52
4 ideal holder 50-2204CT@ $8
Total = $ 270ish USD
Nice thing about this is you can hang each cob/heatsink individually so they would be adjustable depending on the plant size nearest them. You can spend a little more and get better efficiency by going up to the clu058 series citizen cobs, which would work with the same heatsinks, just need different holders.