Yam as 500 in direct comparison with pm 6004 shows more dry, although more diffuse and detailed high frequencies, similar bass punch, but more fatiguing listening overall, for me. I tested this AS 500 for a week at home , but then I changed with Marantz PM 6004 .Yam AS 500 is a very complete amp, but doesn't meet my preferences for a warm sound with my B&W; is a beautifull vintage looking amp, with a lot of features, but no good vol and tone knobs and a delicate front plate for fingerprints when you touch ...Yam as 500 has loudness too and in direct comparison with pm 6004 shows more dry, although more diffuse and detailed high frequencies, similar bass punch, but more fatiguing listening overall, for me. Marantz drives my old B&W 603, like 684, and a ASW 610 sub linked at spkB - highlevel - my room= 30 mq and 90 mc with ease. Just a few thoughts . bye