I am also a 12 year user with the ATI Sunpower with Reefbrites. I am thinking to make a change to Leds as to be honest the electricity bill is killing my monthly expenses.
Apart from price and power that each model produce between the 32 and 64 what will you experts recommend me for my standard 125 6' (72 x 18 x 24) SPS tank and how much?
I think your best bet for SPS dominant would be 4 x 64HD.