Amplifier for Sonus Faber Amati Homage?


Looking to get amplification for my new Sonus Faber Amati Homage speakers. I use a Thor TA-1000 preamp and listen to mostly vinyl (Sota Star Sapphire, Koetsu Rosewood Signature. Half jazz, the rest split between blues, classical and rock. I am quite allergic to any treble brightness but appreciate treble extension if it doesn't create fatigue. That said, I prioritize a rich, real midrange, and like a somewhat laid back stage perspective. I am not a neutrality guy... looking for musical and involving.

Stereophile described the Amati load as "The speaker is a moderately demanding load, however, as can be seen from its plots of impedance magnitude and electrical phase angle against frequency (figs.1 and 2). With a maximum of 7.8 ohms, but a value below 6 ohms in the midrange and below 4 ohms in the bass and high treble, a good 4 ohm-rated amplifier will be called for."

Any wisdom on amp choices? Budget is under $4000 used. Tube only please. ;)
Thanks!

montaldo
You need a tube amp with output impedance less than 1 ohm for flat response into the Amati's varying impedance. See georgehifi's response. An older Audio Research tube amp might work. Why not try a hybrid amp like a New York Audio Lab (NYAL) Moscode 150 (75 wpc) or 300 (150 wpc)? A 4 - tube (6CG7, 6FQ7) front end and MOSFET output stage. I own a 150 and it is an excellent amp capable of driving difficult loads like the Amati's. Available on the used market for about $1K. It will give you the best SQ of both tubes and transistors!
I really prefer the sound of all tube amplifiers, preferably kt88, el34, 300b  or similar sound. Are there any that come to mind that could be had for less than $4K used?

Thanks
Not certain if this will help, given the impedance swings of those speakers, but- you could contact either Speltz(or Ralph Karsten, at Atma-Sphere, who offered something equivalent, once) and inquire. http://www.zeroimpedance.com/zeroimpedance_007.htm Regarding your taste for a, "rich" midrange: whatever tube amp you choose, find some NOS, British valves(ie: Mullard, Brimar, Ediswan, etc), to use in your input/driver stage. Generally speaking, they will warm things up, quite a bit.
Devialet Expert PRO. Best line of amplififiers I have ever heard at any price. 
Invocrus005, are you  recommending devaliet for the Amati because you have heard it with the Amati?

Also I am looking for tube amps only.

AirTight ATM-3s...

I have them with the Amatis and NOS Telefunken EL34s..

It is a superb combination... See my system

 

BTW - I bought mine used years ago for $4500 used...

Run them in triode...

you need amazing interconnects as well...

I note that the last reload for the 12 NOS Telefunken EL34s was about 2K though.