Most resolving, transparent amps.

Boulder 2060
Edge NL Reference
Halcro DM 68
Gryphon Antellion Solo Signatures

I humbly submit Italy's Delta Sigma - simply the most transparently pure I have ever heard with shocking, lightning fast dynamics and extension to 3Mhz.

After visiting them last fall, I decided to distribute after hearing the first note. Amazing how it handles piano and voice. Honorable and ethical people, too.

Jim Ricketts/tmh audio

Under $20k? - Spectron Musician III SE

And you just happen to sell that amp Ricketts?

What a coincidence.

Tgrisham and Phd have nailed the term, "transparency" to a tee. Further- If the recordings you are listening were engineered/reproduced with an unfortunate hand/ear- The transparent amp that faithfully reproduces the shortcomings IS NOT the liability, the recording is. The ambient info Phd mentioned is usually lost in most(but the higher priced) SS amps. Again I have to agree with Phd about the BAT pieces, and for the reason he sites: less in the signal path(one reason tube circuits are better- simple topography). That's Victor Khomenko's(of BAT) design philosophy. Placette makes an excellent(all bulk-foil Vishay resistor) passive line stage, IF your sources have sufficient output. I've never used their active(with gain) unit, but it is supposed to be close in it's transparency. Don't forget- there are a multitude of cables/interconnects that will affect your signal transfer/purity as well. I've found Kimber Selects to have the least impact, in my system, after much wire-tasting.