Amplifier for Sonus Faber Extrema


I´ve just bought a pair of Sonus Faber Extrema Loudspeakers and I want to buy an amplifier for them (used).
My actual system: Krell Kps20i CD Player, Sonic Frontiers Line 2 SE Preamplifier, Classé Audio Fifteen Power Amplifier and Audioquest Volcano DBS Speaker cables (biwire).
I want to replace and upgrade only the amplifier and I want to still use the Sonic Frontiers because I love this tube preamplifier. So I´m loocking for an amplifier to use with the Extremas and the Sonic Frontiers.
Some options could be: Classé CAM350 Monoblocks, Krell KSA300S or Pass X250.5
I will apreciate all your suggests and recomendations.
elduende14
Well, I need to chime in here. First of all, nice purchase - i think you will ultimately LOVE these. I own a pair of Guarneri Homage (with a REL sub). Clearly this is different (easirer) to drive than the extrema, but to my ear - having tried various SS amps from Ayre, Rowland and a few others - SF's work best with TUBES!!! I found out that SF uses the amazing Berning ZH270 in their refernece system, so i looked into it, and bought one - AND WILL NEVER go back to SS amps. The sound is simply astounding.

Now, I dont know if a single ZH270 would be up to driving these, but I am sure a bridged mono set would. You should at least consider the amp used by the manufacturer in their reference system....
Typo Correction from earlier entry:

My pair of Threshold SA/1 mono-blocks are on the top end (sweetest midrange & super highs for the Extremas). And my pair of Threshold SA/2 mono-blocks are on the bottom end for incredible bass dynamics.

All with of course brand new BMI Cable HammerHead power cables. And ORCA 2 speaker cables.

Everyone who owns the Extrema's (especially the later production ones like myself); Enjoy them , because they are the best one can wish for a monitor speaker--period !
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I have my Extremas running with a Levinson 23.5 Amp after upgrading from a 27.5 (the 23.5 is double the power of the 27.5.
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Has anyone compared the Levinson 20.6 versus the 23.5 running the Extremas ? I believe the that 20.6 are rated at 100 watts (all Class A) per channel while the 23.5 is rated at 200 watts.
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Thf, as with many tubed amps, especially (this OTL design), the watts/channel rating belies the way it sounds, So, with that caveat, the per channel rating of single stereo ZH270 is 70W/channel - which in my experience on my Guaneri's, that 70W per channel compared very favorably to SS designs with 150-200 per channel range(including my former Ayre V-5x), so a mono block set should be equiv to 140W/channel, and this is capable of driving any load, including the Extremas.....

While not having heard that particular combo, i would bet a lot of coin that it would sound fabulous!