You keep getting not very good amplifiers with tons of power, way more than your easy to drive speakers need and expect a big difference.
I disagree that preamps are more important than amps. I think they're both important. Although to what degree depends on the components and the rest of the system.
With your fairly easy to drive speakers, you should be looking for quality not power. I'd guess that a good but cheap integrated, perhaps even a lowly Trends T-amplifier, perhaps something from Virtue, a Virtue One would slay anything you've tried so far.
I disagree that preamps are more important than amps. I think they're both important. Although to what degree depends on the components and the rest of the system.
With your fairly easy to drive speakers, you should be looking for quality not power. I'd guess that a good but cheap integrated, perhaps even a lowly Trends T-amplifier, perhaps something from Virtue, a Virtue One would slay anything you've tried so far.