I purchased BHK preamp, M1200, and P15 together three weeks ago. The first week they sounded flat and dull, but now they are phenomenal. It may well be PS Audio designed their gears to match well with their power plants. P15 may not give as much improvement to other brands as to their own.
Another huge improvement was adding an Audioquest Thunder AC cord to P15. It made a dramatic improvement too.
Another huge improvement was adding an Audioquest Thunder AC cord to P15. It made a dramatic improvement too.