What improvements did you hear in going from entry level to high end Audio?

Sorry if I offended you, N. But that’s the physics.

There is no component which is pure resistance, pure capacitance, pure inductance, pure gain. And there are other effects, such as dielectric absorption, phase shift, temperature stability, etc. Each component and each combination of components has its own mixture of these, and its own sonic signature. And may be priced accordingly.

To quote Horowitz and Hill, in their famous electronics tome, from the table on characteristics of capacitors,
"Electrolytic: Accuracy - Terrible; Temp Stability - Ghastly; Leakage - Awful".

Again, sorry to offend you, N. But that’s the physics.

The whole wall came alive, versus the sound coming from just the speakers or the lower end half of the wall.

More body and detail.louder without any distortion.Natural timbre. Big improvement in bass. Uniform across frequency range. 

A better audio system allows me to hear with greater detail and resolution, the faint sound of money draining from my bank account!

My first venture into home audio was back in the mid 70s. Quite a basic Lo-Fi system consisting of a Fisher receiver with a pr. of BIC Venturi speakers and a Pioneer TT.
A few years later, while on a road trip, I happened by a Stereo shop and decided to step in. WOW! Large beautiful speakers, the likes I had never seen - Klipch Corner Horns, huge Altec speakers, tall ultra thin speakers they called Magnapans and a whole host of smaller speakers - Thiel, Spendor and others. In addition to speakers, they also had racks of interesting amplifiers and players. After some hours of listening to a variety of systems, I came to appreciate that an audio system actually could sound allot like a real performance in my home.
My current taste in music is broad, but since my preference is for anything with good vocals and live, real instruments - I lean towards electrostats, ribbons and open baffle speakers and somewhat prefer tubes.
Cold, dark and revealing (regardless of how pricey) doesn’t work for me, If it lacks the body, richness, air and harmonics of live music.
My current system (well south of $100K) even though there are some things I’d like to upgrade, along with being quite detailed, manages to click most of these buttons (body, richness, air and harmonics) for me.....Jim