Mono is one I'm curious about. Years ago had a modded m1060. Sound was great but by a country mile the worst built headphones I've ever seen. Nothing that would break, the parts felt durable, but it just felt like the absolute cheapest possible "sturdy" build where yes things are metal and wood and so on, but it feels so poorly distributed weight wise. Feels like a piece of string with 2.5lb weights on each end, just the worst most uncomfortable headphone I've ever wore. Earpads were great but I literally couldn't even look down at my phone without them falling off.