Shadorne, you nailed it. Basically, the tube amps produce varying decibel levels across the frequency band, with the higher frequencies (and the higher impedances) generally having higher decibel levels relative to the lower frequencies (and the lower impedances).
There are several Sonata III owners who happily use tube amps, so it seems we are not all equally sensitive to tonal imbalance.
There are several Sonata III owners who happily use tube amps, so it seems we are not all equally sensitive to tonal imbalance.