Hi have owned both speakers and my answer will start with a question: how large is your room?
Considering the speakers - how do you compare an eagle with a peacock?
The Extrema need some room gain to develop the bass, good positioning and a matching amplifier to start flying. Believe it or not they are also extremely dependent on the cables.
I had the Extrema's in a flat and soon realized that I had to sell them because they are the type of speaker that sounds great at levels you should not listen to when you have neighbors. Their huge soundstage did not collapse with loudness. Fortissimo could be their nickname. If you find the recording listen to the VTL LP or CD "Louis" (VTL 007) at life like levels with them - you will be astonished with the number of musicians that are hiding inside and outside your room.
The Guarneri have a nice timbre and a spacious sound. Tone of string instruments in excellent, as with the other Homage speakers. But they did not feed my soul as the Extrema's did.
The Proprius CD Cantate Domino was very popular between audiophiles when I owned the Extrema - the layering capabilities of the Extrema in the chorus was unique for a cone speaker. Mahler and Shostakovitch also loved them!