Sherod, I, of course, have no experience with the PorterPort. My comparison is nowhere near that done by Dlcockrum on the thread above. He has the advantage of quick a/b comparison. Actually, Dave came here some time ago agog with the Tesla outlet. I was already greatly impressed with the SR ARTs. I approached SR about it and the PowerCell.
I put the PowerCell in first and compared it with my IsoClean outlet driving my Acoustic Revive RTP-6. It was no contest. The sound stage was wider and more precise with lower background noise as well as rising vertically? I have never understood this impression, I must say. The bass was well defined and directional, and the top end was sparkling.
Yesterday I replaced an Eagle outlet on my other dedicated line with the Tesla. After five hours it was obviously also contributing to further improvement with the PowerCell. Best Audiophile Voices was "real" last night, but Sinatra & Basie at the Sands ranged from poor at the beginning to pretty good at the end. The SR combo really exposes the quality of the recording.
I suspect that the majority of the improvement is from the PowerCell, but the little outlet is worth it. I am no longer using the IsoClean, the Sound Applications/Jena Labs, or the R1.
I should also note that I expect great improvements today.