Problem is, I have. I've used $15 Best Buy HDMI; I've used Audioquest cables costing over $300 new. My receiver is a 4K-ready Onkyo with tremendous rep. I've never used more than a 6' HDMI cord from either the receiver or the laptop or the tv. And I really can't tell the difference.
Power cords, however, I can.
Power cords, however, I can.