Need help with Klipschorns/Electronics and mother.

My parents' system consisted of Klipschorn speakers with a Dynaco ST-120 solid state amplifier and a Crown IC-150 preamplifier. This system sounded satisfactory to all concerned for about 20 years. Then one channel of the Dynaco died. Rather than having it fixed, I decided that they needed to upgrade to a Rotel RB980BX amplifier. The sound was immediately worse, but the most obvious problem was a hiss coming from the Crown preamp and amplified profusely through the Rotel/Klipschorn combination. I sent the Crown back to the manufacturer to be refurbished. They sent it back and said it was now perfect. The hiss persisted. I bought a Rotel RC980BX to replace it. The hiss is now gone, but the Rotel preamp has no "loudness" button, and no tone controls to tame down any harshness in the upper midrange/vocal area. The K-horns now sound shrill like they never have before, have no bass, and my Mom won't forgive me, PLEASE HELP! I am actually thinking about having the Dynaco fixed and putting the system back to its original configuration. My Mom would never spring for a good SET amp.

Footnote: Someone please explain why when I reversed the polarity of the speaker wires, the K-horns immediately sounded better (i.e., more full bass). In my estimation I have the speakers hooked up backwards, but they definitely sound better?????
Without getting into all kinds of further permutations of ways to 'improve' this system, my advice FWIW is to go with plan B and give back Mom what she wants. It's your safest, simplest, and ultimately cheapest course of action given the situation, and nothing else you could try to do even with the best of intentions will probably result in more satisfaction on the part of the owners. It seems as if the sound they were used to was dependent upon utilizing the loudness contour and tone controls of the Crown full-time, and that the new amp presumably has more gain than the old amp, which didn't highlight the hiss from the old preamp so much. Quit while you're still within earshot of being ahead, and beat yourself a hasty - if wiser - retreat to the status quo.

As for the speaker hook-up polarity deal, to get the change you observed you need to have reversed only one speaker's leads, which would put the two speakers in-phase with each other if they had been out-of-phase before, resulting in stronger bass response, as well as correct stereo imaging. Changing both speakers' hookup polarities at the same time will reverse the absolute phase of both speakers together (something not audible for the purposes of this discussion), but would not affect the relative phase congruity between the two speakers. This all tranlates as, just make sure the two speakers are hooked up the same way as one another at both the amp and speaker ends (+ to + and - to - *or* + to - and - to + for *both* channels), or if you can't easily look behind the speakers, just go with your ears.
I have hooked it up + to - and + to - for both channels and it definitely sounds better than having it hooked up + to + and - to - for both channels. I didn't think this should make a difference either, but it was very noticeable to all. Maybe we just improved a connection?
That is certainly possible - the only way to find out is to switch back and see if anything changes.