- I would try borrowing better speakers to compare your current speakers against - using your AVR amp.
- And/or/then borrowing a different amp to power your speakers
- Alternatively you might be able to drag your speakers to a shop to compare them to other speakers… and that will also let you listen to their electronics through them.
With luck that should give some insight into things… More insightful IMO than just buying various gear… if you abide A/B comparisons.