I inserted the Burson AB160 RCA into my system (between the pre and amp) about a month ago, and I'm very pleasantly impressed (actually stunned) by its performance. My system is very transparent, highly articulate, and reproduces the musical emotion of the performance extraordinarily well. Over many years of experimenting with different components, I settled on the Placette Passive Preamp as the pre that provided my ears the most transparent and life-like articulate sound. The Placette worked well in my system. I had none of the negative characteristics (lack of dynamics, dull hi end) commonly ascribed to passives. However, I had my SACD player upgraded by VSE and its output voltage was reduced significantly, lowering the system's overall dynamics. I lived with this for several years while trying to compensate in other areas, eg, focusing on room characteristics, reducing AC mains distortion and noise, system vibration, etc. Although these adjustments improved the system's ability to reproduce music, I felt that its dynamics were still somewhat lacking. Since the Burson Buffer is inexpensive and had been reviewed most favorably, I thought I would try it---I had been considering it for some time, but thought it would lower the system's transparency, a characteristic that I highly value. Another factor that motivated me to try the Buffer is similar to yours: the Placette has an output impedance of 300 ohms and the input impedance of my amps (Odyssey Extreme Mono SE) 10K, not an ideal match. This, I thought, may also be interferring with system dynamics.
In spite of my reservations about transparency and adding distortion from another component, I tried it and it works beautifully. Surprisingly, I have loss NONE of the previous transparency, at least, I cannot detect any---hard to believe, despite the insertion of an active component and another set of 3' interconnects and all of varibles these two things inject into the system, but for some reason I do not hear any degradation of the musical information. It's a mystery to me. Dynamics in spades. Note: the buffer boosts the signal by 6db; when testing, be sure to compensate for this.
In short, I have no plans to remove the Burson from my system. I am quite pleased with its performance (remember: I've only had it in my system for about a month, but so far it has been great).