???What's The LEAST Expensive "End Game"Amplifier You've Ever Heard???

I love my Arion Audio S500.  Shoebox size digital switching amp designed and built by Mike Kallelis.  500 watts per channel, super clean, neutral sound.  Plus, it weighs only about 22 pounds!  Price should be under $3000.  A real bargain, and I can't see myself ever replacing it in an attempt to upgrade.  If it ain't broken...

Amplifier Circlelabs A200 -  on the SAME level as Gryphon

The Pass Labs XA25 is one of the most 'transparent' amps and a reference for many reviewers. Audiophiliac, Stereophile, Absolute Sound. I have one paired to Harbeth 30.2 40th and it is a match made in heaven.
Last week i was auditioning speakers and the store owner told me that a customer had recently changed his entire set up 5 times more expensive to go with the XA25 because he liked it so much. 
At about 5k USD , you cannot go wrong. Built like a tank, sound like velvet.

When I bought my Simaudio 340i, I was auditioning it against the Bryston B135 cubed and Cronus Magnum III.  I picked it because it's really musical, has great current capability resulting in excellent woofer control.  A really neutral, very capable amplifier section.

My analog section consists of the 340i phono stage being fed by a Graham Slee MC amplifier connected to a Mofi Ultradeck/AT-OC9SH cartridge.  The digital side is a Chord Qutest feeding the single ended input of the 340i.

At this point there are many things I'll upgrade, like cables etc., before considering replacing the 340i.