24 should be plenty, I don't know if I would use that HS though...It would work fine but if you want all SPS I personally would keep the LEDs closer together in the center of the tank to allow for higher PAR numbers in center and lower towards the outsides. That would allow for a wider range of PAR throughout the tank. I would go with 60 or 80 degree lenses, 40 would increase PAR but you wouldn't have as much coverage. The meanwell ELN-60-48d drivers will work great, you will just want to adjust the max output for the one for the blue LEDs or not run it at 100%. The factory max output is like 1.3A and the XPE leds have a max of 1A