I'm going to say mid-fi for a couple of reasons. First, Adcom is pretty good, but It's built to a price point and it's price point peers probably wouldn't be considered terribly high end. Second, JBL themselves consider the 500 series a mass market product apart from their Synthesis line. You won't find them in a Synthesis dealer or on the Synthesis website.
And just to be clear, I'm using an Adcom pre-amp, and it's pretty good, but I know there are pre-amps with much better noise and channel separation.
And just to be clear, I'm using an Adcom pre-amp, and it's pretty good, but I know there are pre-amps with much better noise and channel separation.