I'd throw a cxb3070 3500k or 4000k on there. Should be close to 6k lumens. By itself, on the high end of flowering a 1'x1' space or low end vegging 1.5'x1.5' space.
They do I would go with the 36volt for wattage efficiencyI would love to convert my "real" "old model" Mars 300w(180w) but it uses 4 drivers rated at(output) 55v-100v and .55-.6A so I don't know if they have the power to push a cxb3590 COB.
I believe you can run 2 to each @Atulip is the guru on that but in looking what you wrote you could use them to run 2 of the 36 volt per driver yes.. Attaching them to a heat sink would allow you to cover your space and you could add one red and one blue little cob if you wanted as well make it really custom@Ripper that is good to know. So 2 36v cxb3590's on each driver correct? Maybe I'll just pull the drivers out of the old Mars fixture and mount them up to a different heatsink and use what I need. I am only working is a 24"x36"ish space.
2 36v or 1 72v per driver. The one cob would be cheaper but 2 would be more efficient. Few options:
1 x 72v cxb3590 @ .6A gets you ~7,800 lumens at 41w for around ~$50
2 x 36v cxb3590 @ .6A gets you ~8,200 lumens at 39w for around ~$100
2 x 36v cxb3070 @ .6A gets you ~7,700 lumens at 40w for around $60
The "new" Mars300(60x5), 2 of the ones I converted had the exact same drivers, just 2 drivers per light though. Running both 2 x 72v cxb3590s in one and 2 x 72v cxa3590s. The best bang for your buck is gonna be the single 72v per driver.
They do have the same light output at equal watts. But the driver is only gonna push .6A through there, so the 2x 36vs will be 20w each or so compared to the 1x 72v at 40w. And higher efficiency since they're running lower watts per cob, but it's a small increase in efficiency for a large price increase for 2 cobs.