Hmm, it has been a long time since I've upgraded anything audio wise. It was probably adding the Emotiva UPA-7 amp to the mix. Been so happy with the system since adding that several years ago, I've had no need to upgrade. Next will probably be a new sub since my M&K MX350THX MKII is well over a decade old, and I don't take it easy on that thing, but it still has a several years of life left in it.