The design is different. The 7500's amp channels are class A/B all the time, I believe, while the 2200 transitions from A/B to G at around 80W of output. Also, the 2200 is a true monoblock (one power supply for one amp channel), while the 7500 has a single power supply (or perhaps sort of two, since there are two transformers) for the five channels. I've found the differences to be very subtle between my 7500 and my older 200's, with my preference being for the 7500 by a narrow margin.