The PLB-AMP8 from your thread title is the AMP. This is possibly the one piece you wont need to upgrade as long as its working properly.
What does the existing system do? What do you want it to do?
Distributed Audio only? What sources? Have you thought about using Sonos?
Distributed Video? Chances are your existing system is not HD. Are you wired for it?
Lighting/Climate Control? do you currently have control of these sub systems? Do you wan to continue to have control of them?
Dennis Erskine, I will trade you a broken palm pilot and Cubs tickets
Quality Control at Phast was awful. 20-30% hardware failure at installation cost us a lot of money. Sure.. after the 3rd or 4th keypad you might get lucky and find one that communicates and has a working LCD but who can stay in business experimenting with an unfinished product?