I installed PS Audio Power Port in the wall (hubbell 8300)and got PS Audio Ultimate Outlet (high current) version which sets on the floor for my amp , got much more open/3D sound for my efforts. Hard to isolate what difference the the PS Audio wall outlet made, but you really notice the much tighter grip it has on plugs inserted in this unit. Also when installing wires to Power Port I cleaned the oxidation and used Kontak before re-connecting.
In the literature PS Audio makes a big deal about the 15 coats of polished nickel plating and claims this is much better than standard brass contacts. I am sure if I took the time to try other wall outlet brands subtle tonal differences would show themselves, there was even a thread here recently where author claimed he could hear difference between plastic, brass, or no cover plate on AC outlet.
In the literature PS Audio makes a big deal about the 15 coats of polished nickel plating and claims this is much better than standard brass contacts. I am sure if I took the time to try other wall outlet brands subtle tonal differences would show themselves, there was even a thread here recently where author claimed he could hear difference between plastic, brass, or no cover plate on AC outlet.