Basically the new models have silver back-labels.

I remember getting some Alpha 8s recently and I saw that label, I think it had a rocket ship on it...

"As a result, power ratings have improved by up to 100% or more in some cases. The Kappa models, once rated at 400W across the board, are now rated at between 450W and 600W. The Alpha models, once rated at 100W, are now rated at between 100W and 200W. The Beta 15 was originally rated at 150W but has been re-engineered for a massive 350W! To recognize these new models, look for their chrome back labels."