Best amp under $6k, in your opinion?

Hello Perrew, Mk2 is the same Spectron in the sense of the speaker control. There are small improvments, of course - bass is tighter, faster - imaging is sharper.
Where Mk2 shines its the midrange (and highs) - literally SET midrange - many people who own both can tell you the same.
Good Luck
Rafael
P.S. Atm-Sphere is also great amp but only, only if your impedance is never lower then 4 Ohms

Pass Labs X250.5 or X350.5

I think SP uses Belles amps to voice their speakers.

After owning several Belles amps and others mentioned here, I must tell you one amp stands head and shoulders above the rest.

Get a trl D225 stereo amp as it is the best amp for your speakers. I can say with 100% confidence you will not find any amp under $6000 that sounds as good.

Amazing amp that breaks through the sound ceiling I thought all home stereo was under. After owning and hearing amps in my reference costing up to $14,000 the trl was a complete revelation.

I know I sound over the top, but after just a few minutes with this amp you will experience what I know.

Bill

I was wrong about Belles and SP speakers. I was thinking of another speaker company - Source Technology.

Sorry

Bill