The thickness of the power cord does not mean a thing. What matters most is the design and material used and how they, in combination, can effectively minimize external interference.
Those looking for quality, effective power cords I highly recommend checking those from Audio Art Cable. I recently tried the mid-tier Power 1 Classic cord with the Furutech plug set and I was blown away at the difference it made to the overall sound quality of my setup. The reviews from 6 Moons are accurate (for once) and the difference was like night and day. Increased resolution, detail, deeper bass and instrument placement. I could not believe my ears as the difference was akin to a component change. I am now in the process of replacing all power cords in my system from Shunyata Venoms to the Audio Art SE cords.
I believe there is a promo going on now with Audio Art cords with the base cord starting at $130 with Wattgate plugs and free shipping which is incredibly good value. I believe the higher end cords use the exact same materials with the exception of the plugs being different. Grab these for a song while you still can..you may be able to get a better price if you mention Tim from headfi recommended these.
Edited by DarknightDK - 6/18/14 at 2:09am