I've been thinking and my brain froze... If you want the best of the best from ATC, you need to buy the SCM70 ASL's. It is the Ultimate and only reference for folks with obscene amounts of cash. They have to match some 40 pairs of MOSFETS exactly. This alone takes like 4 days of labor! The 70's are fully discreet ClassA amps. Same drivers, but the amps are where the more money is going. You will get the single best sound from the 70's. They're very contemporary looking, but you can choose from like 4000 different coverings.
The bass driver is a 9", same as the 50's, but the amazing fully discrete amps and silver wound voice coils raises the price from about $14,000 for a pair of Active50's to about $24,000 for a pair of Active70's. The sound of the 70's is the best sound that you can get. Even at around $27,000 for a pair of 150's, the Active70's are the best sound that you can buy. I'm also not exactly sure if they still make the 70's as they are so labor intensive and time consuming that it's a complete pain as I understand.