Interesting thread.
I've done some hands/ears on research here with my system and after several rounds I have settled on Oyaide R-1 outlets which clearly sound best with my gear. The outlets I have tried off the top of my head: Cheapo Lowes, PassSeymour Hospital Grade, Porter Port, Wattgate 381, Furutech GTX-D, MIT Super 20 (more of a conditioner since it contains filters).
They all sound very different so I think it would take some trials to determine which you prefer. I also think it's important to note the differences are not subtle. I would never have imagined this to be the case without putting in the work to find out for myself.
"There is a principle which is a bar against all information, which is proof against all arguments and which cannot fail to keep a man in everlasting ignorance that principle is contempt prior to investigation." Herbert Spencer