supplemental lighting for hlg 550 in 4x4?

I've had the HLG 550 for a couple weeks now and it seems to have taken the place of Bestva 1800 (foreign junk) and Mars II 700w without issue. i'm moving up in the LED world. I've still got advanced p300 and I'm looking to return it and spend that money on new, more efficient tech, particularly in the DIY/latest tech space.

My current grow is 9 autos. I have a 4x4x7 tent. Everything but one is in soil.

I'm just starting to break out into the non-mass produced, sales cycle lights, so give me a break. I'm considering a cree 3590 set up. something kinda simple. I'm Looking to buy the kit this time around because I'm still not confident in my ability to match drivers (Im learning quick, but theres an overwhelming learning curve between plant biology and light recipe, etc), but I'd like to get my hands dirty, especially if it'll save me some money.

If there's anything that I should be considering other than cree, please let me know. I cant reallY spend more than maybe $375

If you really want to try cobs and are going DIY. Checkout the Cxm-22's from Cob kits. Or perhaps a Vero 29 kit from cutter electronics

Either of these will be as efficient as the crees at much better price. Cobby will help you with any questions you have about drivers, great service. The cutter kits are ready to go.

Either of these options require you to build a frame. Rapid LEDs cob substrate is another framing option.

But as someone with all of these thing in my photon arsenal (crees from cutter, QB's from hlg, cxm-22's from cob kits) I'd just buy another quantum board kit personally. Or not as a hlg 550 is perfect for a 4x4