The 16.4.2 and the 16.4.2 Ai are completely different animals. The Ai series have an actual computer built right into the mixer...there are other changes that result in faster and better audio quality. Therefore, the 2 mixers cannot be cascaded.The Ai doesn't need a computer for remote control via the Ipad, or updating. There are some other things as well and I think there is a comparison post in the Knowledge base...