The only thing I not happy about this RX3 is the volume imbalance issue at low setting. At cold it's worse, after warm up, gets better, but I still paranoid about the imbalance thing as it made me feels it always imbalance even after warm up or crack up the volume its get to the point of indistinguishable.
Mine doesnt suffer that issue although I dont use it with IEMs (occasionally IE8's) but mainly full size cans. I'm annoyed (but tolerate) with the scratchy volume pot so be warned if you suffer from OCD you may have an issue here. For the hell of me I cant tell if its the RX3B or the -dB or the combination. What I will say is the SQ trumps the issue hence why I still have them.