Not only does the 6900 have an equalizer but it has a loudness switch that will compensate for the Fletcher-Munson curves at low volumes. I wish my current preamp had one.
I am only familiar with the 8200 mk2 but as I recall, their sound is more similar than not: a little warm with good coherence. However, I think the 6900 is clearer sounding and has better definition. Can't go wrong with the Mc IMO. If you don't like it, you will get what you paid for it (if you buy used) so there is no reason not to try it out. Good luck! Arthur
I am only familiar with the 8200 mk2 but as I recall, their sound is more similar than not: a little warm with good coherence. However, I think the 6900 is clearer sounding and has better definition. Can't go wrong with the Mc IMO. If you don't like it, you will get what you paid for it (if you buy used) so there is no reason not to try it out. Good luck! Arthur