My feeling is that AMPLIFIERS are the weakest part of the whole chain. They always have been, in my audio experience going back 50+ years.
The amps are FAR worse than the speakers.
In 2019, I find that 99% of the amps one can buy, don't cut the mustard. Also, VERY few people, active in audio, have long-term heard these amps in the 1% bracket.
The best sounding amps, IME, will be 2 Watts or less, tube, with absolutely NO negative feedback loop. Only from this amplifier topology have I heard playback that is long-term satisfactory to me.
You pick the amplifier first, ................and the rest of the system follows suit.
The speaker will be a two-way, highly efficient / sensitive, in the 99 to 101 dB or higher range, and the woofer will be a 15 inch. The speaker's enclosure will be ten cubic feet as the minimum size, no open baffles. ALE, GPA, or some vintage ALTEC drivers can be used, with care, slight mods.
To obtain maximum dynamic contrasting, and wide band response, the audio wire will have silver content, and I like to see multiple paralleled wires, the total equaling about 8 AWG , per polarity, for this 2 Watt amp. Use of 8 AWG equivalent wire STARTS inside the amp, with the Power Transformer's High Voltage winding's center tap, and it extends, amp-to-crossover, through the crossover, and all the way to the voice coil terminals of fifteen inch driver.
The "ultimate" useful amplifier topology will " only and always " be simple - as follows : Two Stages, Direct Coupled, either SE or in Push Pull, using triodes. This topology is hard to find, done really well, so I DIY design and build my own. Its a lot of fun. Good luck in your quest.
Front end ( source ) equipment in 2019, is NOT the weak link. We have some very good sources these days, if selected intelligently. Amps that are truly superb, as always, still in my opinion, remains as the problem.
Dowto1000