Got most of the parts for the 2540 build (4000k colour temp). I am still waiting for the 60W drivers so fired them up with some 50W units.
It runs super cool at 31C after 30min so hoping with the 60W drivers it will stay below 40C.
Forgive the 'raw' state of the build, but it has to be disassembled when the new drivers arrive anyway.
With all new parts (still have to buy fans) it works out to about $75USD and generates 13000 lux at 50cm (130W from the socket).
My 'go to' light is a full spectrum white 1500W COB unit (230W from the socket) and interestingly that outputs the same lux, but at 76% higher power usage.
In $$$ terms assuming 16hrs per day at 25c/kwh the 1500W unit costs $0.92 per day vs the 2540's at $0.52 - In theory the build will pay for itself in 267 days.
Might need to rethink the setup now ....