Pro models sonically behave the same as consumer models. However, pro models are in a different cabinet- an MDF cabinet painted black. This usually leaves consumers unhappy as it will have multiple visible flaws. We've had an audiophile try to buy a pro 20 to save money over the classic 20 and sent all three pairs back over a cosmetics (turning them all into B stock although they were all perfectly normal). Pros don't care about tiny nicks or irregularities in paint. Pros want the cheapest possible cabinet because it will get banged up anyway after a few years of use. Most audiophiles do not understand this and think they should all be "assembly line perfect" even though ATC is small production handmade product.
Consumer product has nice finishes and carefully built cabinets.
Brad