What 2 channel Amp would you Buy for $6k?

Quicksilver v4 mono blocks

Sanders
Benchmark AHB2
Coincident Frankenstein MkII
Bryston cubed series
FirstWatt
Pass XA30.8

depends on taste, power need, gear etc

Roddyboy , I think your question is strange , would you not choose the best amplifier to mate with Speakers you use ? I would think most would research this with other owners or even the manufacturer of your speakers , correct me if I’m wrong but isn’t that how it’s done finding the best amplifier that will drive your speakers optimally ? 

Something in the Pass Labs lineup would work very well, depending on your power requirements. I love my Xa30.8. One review says that it competes with a highly regarded SET  amp (can't remember the name offhand) that sells for over 20k, plus you get the firm low end punch that comes with SS. It's very conservatively rated at 30 watts. It's easily driving my Vandersteen Quatros. I bought mine used for just under 5k.

My speakers are Magnepan 20.7s

Amps I have had 

Mcintosh 452
Sanders Magtech
Bryston 4b3

Of all of those the Bryston is by far the best, the worst is the 452, weak base on the 20.7s and not a great sound stage.