If I understand correctly how amps improve SQ, there are two ways: 1) increase the impedance of the system similar to adding a 75ohm adapter to ER4P; 2) to reduce clipping during peaks.
I am sure an amp can improve SQ a bit due to 1) but 2) shouldn't play much a role for light Jazz.
Am I right???
+4 on the low amplifier output impedance, the lower the amp output impedance the better. This is not digital transmission line where "impedance matching" is important or desired.
A very good amplifier just SOUNDS better.
My AKG Q701 'phones sound awful direct from my notebook computer or iPod and sound merely OK direct from my iPad.
You don't have to spend massive bucks............I like the sound I get out of my iBasso D12 DAC/Amp combo.