Sonus Faber Guarneri - will any aiddtional isolation be beneficial?

I’m using some Soundocity SEV9 with my ProAc Studio 148s. Spikes to metal floor protectors on top of hockey pucks. Works very well with the bottom porting. Might put some thin granite slabs between the pucks and carpet

As your speakers are new, I would listen for a few months without changing anything. After that, IMO, there is absolutely no way to predict what effect  changing the footers will have without trying it. There are too many variables to be able to say which footer will sound best to you. BTW, those are absolutely gorgeous speakers. Just a note about Symposium, I tried the slim platforms under my Opera monitors and found it made them sound too thin in my room. This might have been good if they had boomy bass, but it didn’t work for me. Just try to enjoy. Really.

Chayro,

I completely agree.  As with any sort of "tuning" whether the result is positive or negative is dependent on a whole lot of factors that make it impossible to predict the outcome.  That is why I recommended some kind of cheap and rough experiment first before paying for very expensive isolation options.  By damping resonance, isolation devices will tighten up the sound which will most often mean a leaner sound; it is hard to say whether this will be "better" in any particular application.