Speaker Efficiency

You may have a low quality alps volume pot ,just look it is a round silver can it is only 2 wipers with a contact spray , once it gets past a certain point it can start loosing resolution , where a resistor ladder type ,or rely much better ,also 

for that speaker the Sonus Faber go down to under 3 ohms you need much more power then that ,the Klipsch are a good fit ,I rebuilt a bunch Klipsch speakers 

the stock internal Xovers are very low quality ,even crites  Xovers which were in it 

not that great the Xover is the ♥️ of the speaker ,having owned a Audio store 

and modding my own Xovers and others for years ,,if you plan on keeping the Forte 

then I highly recommend doing this even theForte 4 cheap Xover parts , once upgraded sounds much more detailed and refined in another league.

the Sonus Faber too could use better Xover parts just unscrew the Bass driver , and look inside , Thst speaker needs a EL34  pentode amplifier .

please remember if pushing a speaker peaks can hit 10 x  more on peaks ,that’s why it’s so e important to match the amp to the speaker .

One thing I forgot Tom mention ,on efficiency of the speaker, Klipsch forte say 99 db actually closer to94-95 db efficiency 

the Sonus Faber you say are 88 DB efficient , for every 3 db it takes 50% more to get to the same volume level  ,the Sonus Faber take over 100%  more amplifier energy to reach the same volume level. Buy a SPL meter on Amazon for maybe$30 for a decent one to know exactly the db you are using ,

then at what db when the amplifier most likely is over driving and Transformer 

saturation is causing it to distort. Either upgrade the Klipsch ,or buy a much bigger amplifier,  the Quality and size ofthe transformers means Everything 

if you want excellent quality without major league pricing, Lookup 

Radu Tarta , one ofthe best custom Amp,preamp designers in all NorthAmerica , he uses Quality like Lundahl chokes and Transformers  , in the  decware a smaller type lower quality , Radu has built several Amplifiers and  preamps for myself .

not cheap but built to last a lifetime he is the-best especially SET amps

which are 8 watts ,or a class A parallel feed using4  power tubes you can get 18 watts . All depending on your plan and budget. Much more$$ though 

for sure though the SF speakers Waay underpowered.

So much goes into the design of an amplifier.  Transformers, power supply section, parts selection, etc.  Audio Note, V-Caps, point-to-point wiring, copper chassis, etc.  Then there is the implementation to reduce the noise level.  In typically lower priced amplifiers, there are limitations based mainly on those factors.  Mid-range may sound fantastic but the overall bass and high end extension are limited.  Most people don't here the limitations until they have a direct comparison from something that is not limited in sound reproduction.  Just spend a day at a local dealer and we were discussing this within the various brands of manufacturers he offers.  Even between the lineup of some manufacturers you can hear the transformers influencing the sound and not always the more expensive unit was better.

Good into here though.

I have a 300b Amp driving my Forte and it is a great sounding combo but it will run out of steam if you push it....which I don't.   The sweet spot for those amps are a few watts, not their full rated power.   

Those same speakers will play considerably louder with my Quicksilver. Amps that are 40 watts but they lack that beautiful tone that my WE 300bs have.   

I have a pair of Sonus Faber in my bedroom powered by a 40 watt Cyrus Integrated Amp.   That Amp drives the SF easily but being 85 dB sensitive they aren't the best match.  Again, they sound great until you push them.   Those are being replaced in a few days with Omega speakers that have a sens of 94.5 dB / w and should be a better match.    

I like low power amps but it limits your choice of speakers.   A lot.   I could see where Forte and a 300b amp would not be a good match,  it's not a lot of power and could be a problem with large rooms especially if the owner likes to crank it up.  Those amp's "forte" is awesome tone, not  high volume levels.

Raise your hand if you're just repeating what a dealer told you to sell you a more powerful (and more expensive) amp?