I’ve not heard that one but I have a 545II ( $300 used) that I use daily in my office with Saga/Bifrost front end and have no complaints. The 5503 was designed for home theater so it has a healthy amount of capacitors in each circuit so it does not fall apart with quickly changing dynamic loads. Power hungry speakers would like the wattage and reserve that it has. However at $550 and the fact that you have no need for it to be 3 channels, there are other used items I would look at. I have not A to B compared them (although I do own one as well but it is currently set up with balanced input cables) but I would think a used Crown CDi would be money better spent. See the Crown thread on this forum. If you tell us what you are going to use the amp with, additional suggestions might be forthcoming.