Why does the Sunfire TGA 5200 Amp Sound So Good?

I am using the Sunfire TGA 5200 with Emerald Physics SC2 Speakers and I am blown away by the sound quality.

Previous amps:

Similar great performance but with different sound attributes (but ran hot for my room):

McCormick DNA-225 Platinum Mod By SMc Audio

Belles 350A Reference (not as good as the DNA-225 Mod), but great upper bass.

Not as Good:

Wyred 4 Sound 2 X 125, 2 X 500 Watt 4 channel

Ayre V-3

Linn Klodt

Jolida 302B (tube)

Jolida 1000B (tube)

PrimaLuna Hifi DiaLogue Two Integrated Amp(tube)