Best powercables for Martin Logan 15A speakers

Use anything that's well made at a reasonable price. High end power cords won't have any impact on sound quality. 

I agree with mgreen27. Power cords have little potential to make a difference unless there is a fault with the current cords. Remember the power has traveled many many miles through all sorts of electrical cables and the expectation that the last meter of cable is going to change or improve it seems unlikely to me from an engineering point of view.

I just use some generic 1 meter 14 AWG cables for my Montis.   My outlets are close to the speakers, so no need for any excess cable length.   If you are plugging directly into a wall outlet, no need for anything else.

The stock ones.  Unless your pet rabbit chewed them up, you need to just enjoy the speakers because a power cable will do zero.

Period.  Enjoy the music, or get a new pair of speakers if you can't.

When I own Quest Martin Logan Kimbers and MIT z cord the white one, did improve the sound a lot, it flesh out more music....I don't remember the kimber model but pk 14 might do it, try Pangea ac14 as well they are good cables...