ha ha joke then lol, I was wondering though if you used 1 old together with 1 new one would this mess up the spectrum? Have you ever tried using a led with a HPS light or different combinations of lights. I know you love a good old experiment lol in reality Its pointless though due to electric cost I know but just out of interest >?
Combinations of any decent horticultural lighting will work well just look at the Kings grows the only light source he hasn't got indoors is the sun lol.