Or the fact he listens at audio levels that OSHA has some serious issues with…
Stay away from Audio Science Review,. you’ll end up with crap if you buy based on the recs from that place.
Have you given a budget yet? How about powered or unpowered? We really need this info to give recommendations.
If you have any kind of modern motherboard, it should have a good enough DAC output to drive an amplifier directly.
If you want to use your old Klipsch speakers, you can probably get away with running them on a lower power amp since they’re floor-standing speakers. I’ve always used old Yamaha Hi-Fi amps, because my dad restores them, but you can really get away with almost anything that is designed well.
The main things I would look for is finding an amp with a good power supply, and one that offers a built-in speaker protection circuit.
Most of the best sounding used amps will be Class A/B, but most of the new options will be some form of Class D. I don’t have much experience with Class D outside of automotive use, so I can’t vouch for their sound quality, but the new ones are almost indestructible now electronically.