Sound replay on ES ranges is far better on a hifi system.
And ... the quality of timbre is far more superior than on QS range.
As for me, when I was about to buy a MD deck, I checked the sound (ES vs QS range) in a sony store simply with a good AKG headphone.
The gap was so obvious (5 seconds listening) that I bought the 20ES. Es range competes with good hifi stuff.
I am since very satisfied with my MDS-JA20 ES.