I don't know much about the SB6580, but I had a Zoom 5341J for a short time and now have a Motorola SB 6141. For the short time I had the 5341J I think it was about the same as the 6141, signals, speed wise. They are both 8 down and 4 up. The zoom crapped out on me in about a week so got the SB6141 and couldn't be happier with it. Rock solid and not a burp. I also noticed the Zoom ran hot where the 6141 is just warm to the touch.