Not sure what you mean by upgrade as the HAP-S1 is sold without speakers, at least in my local market. That said, I do use the Sony SRS-X9 Ultra Hi-Res Bluetooth Speaker. It is compact and accepts inputs well beyond the needs of the HAP-S1. I chose it to address space limitations, accept input from the HAP-S1, my Mac Pro, and bluetooth from assorted portable devices. It has exceeded my expectations and, for the most part, Sony has been good with software updates for it along with the HAP-S1 and apps to remotely operate the entire system. While I am pleased with the HAP-S1 as a source, best performance is by feeding the HAP-S1 with optical input from the Mac Pro and back out to the high res speaker. The speaker has an on board amp and is connected by line out only so the HAP-S1 amp is not in use. Don't know if this will help you but it is one of the alternates for the HAP-S1.