Vitus versus Gryphon

A manufacturer that doesn't get much coverage stateside is Grandinote. Take a look at their Shinai or Prestigio integrated amplifiers should lower power output be acceptable. 

I also second @thyname 's recommendation for T+A ,  as well as both of your choices in Vitus / Gryphon.

All the best.

Gryphon and Vitus are both great amps.  I demoed both the Diablo 300 and the RI-101 and liked the RI-101 since it was a bit more organic and fit the sounds signature I have been looking for for a while.  The Diablo was great, just felt that it sounded a bit harsh on some songs. If I was to guess it was from the preamp side not the amp.  I felt the RI-101 combined the full body sound like tube, with clear/crisp highs, and tight controlled bass.  I have never heard anything quite like it.  I can only imagine how good the SIA-30 is.

If you like more forward vocals then you may like the Diablos better.  It’s a total personal preference.  

A very good comparison summary of the Vitus integrateds
 on Lotus HiFi website in the Blog section.
Vitus will not give you a "front row" presentation- it is more mid hall , balanced with great depth and tonality. Plenty of slam imo.
I heard the Diablo 300 with Wilson and it was very good..maybe a little dark/earthy. Ultimately, and I know this is pretty petty but I just did not like the looks of the Diablo. Looks cheap with the plastic fascia and oddly shaped. Silly, right?

nasaman OP
Vitus versus Gryphon

Your SF’s have an evil load right through the bass

Stereophile: The speaker is still a demanding load for the partnering amplifier, with an impedance magnitude that drops to 2.5 ohms throughout the upper bass (fig.1). There is also a punishing combination of 4 ohms magnitude and –50 ° electrical phase angle at 70Hz that will suck gobs of current from the amplifier.

https://www.stereophile.com/images/archivesart/1207SFEfig01.jpgT

I don’t know about the Vitus as nowhere, does it state what it can do wattage wise on the bench into 8 4 then 2ohms loads, and if it’s Bi-polar output or Mosfet, it’s an unknown especially into these magic speakers of yours if driven right.

With the Gryphon’s you know your getting an amp that will breath easy into 2ohms all day, and that’s because it’s bi-polar output huge power supply and very well designed.
Your speaker at 90db will love the Diablo 120 or even better the Diablo 300. And they sound just like what you said you like you sound to be.
https://gryphon-audio.dk/shop/integrated-amplifiers/gryphon-diablo-300-integrated-amplifier/

Cheers George

nasaman OP

I searched a bit harder and found a PDF from Audio Esoterica which states, "the output stages of the RI-101 are two bridged amps per channel." (Good reason to keep that quiet, and why there are no low impedance loading figures)

Audio Esoterica RI-101
One aspect of the circuit design that has not changed is the topology of the output stage, which is bridged (aka ‘balanced’), which in this implementation means that Vitus is using two separate amplifiers per channel, with each amplifier powering one leg of a differential signal. This circuit topology means twice as much voltage swing and twice as much power (theoretically four times the power), plus lower noise. However, it also means twice the distortion and twice the output impedance (and therefore half the damping factor).

If this is the case then stick with the Gryphon/s as the worst thing that happens when amps are bridged is they loose current ability, damping factor and stability into low impedance’s, and that’s what you have and need with the SF’s as I showed.

Cheers George