When I was in HS, my system consisted of a Nak receiver and used a portable top of the line second generation Sony discman as source. Theoretically, using portable diskmans as source has a great advantage over regular cd players.
The power supply of the portable discman is dc based, at least my Sony with Ni-Cad rechargeable batter was. This makes for cleaner and less harsh sounding music compared to mass market cd players with lesser power supplies and stock powercords. It sounds better than the CDPXA7ES when used with a headphone, but the output voltage was too low on the portable unit to power a Sennheiser.
I had absolutely no problem sonically with my portable unit, but it was pilfered from my dorm room. And I replaced it with a CAL Delta and Alpha with a Meridian dejitter with about $1000 worth of powercords, and digital and analogy ICs.
Ok, in summary, prepare to spend big bucks to get that jaw dropping WOW.