Decided to pimp my nearly 19-year-old RD600 and boy am I happy with the results. Put in an Aguilar noiseless J4 neck pickup and MM4 pickup, OBP-3 with active/passive switch, mid/range control (push/pull), stacked treble/bass, and added passive tone control. The latter was honestly not a bad choice at all - sounds amazing and the passive control adds a lot, making it great both active/passive mode. Just waiting for my new stacked knob (the other size didn't fit on volume/tone)