I have a P-10, and I love it. PS Audio is a great company with some of the best support in the Audio world. I wouldn't hesitate to upgrade your P3 as long as you can afford it. To me my P-10 not only protects my gear, but being a power regenerator certainly provides added benefits sonically.
PS Audio Power Plant P3 to P12
I currently own a P3 which I use for all my source components. PS Audio is currently having a promotion on the P12. Anyone made this transition?