Bel Canto S300 with an Audio Research LS3 Q's

Anyone use this combo? How would the detail, Sound stage etc sound?
I have a similar but significantly different setup.

I have an ARC sp16 driving a Bel Canto ref1000mkii.

This is a very good combo.

Impedance matching between pre-amp output and amp input is a factor that can effect the sound. Tube pre-amp output impedances tend to be higher than SS. Generally, you want pre-amp output impedance to be low and amp input impedance to be high for low distortion.

The ARC LS3 output impedance spec is similar to the sp 16, around 250ohm.

ARC SS amps designed to work well with their tube pre-amps generally have over 100K input impedance.

The BC S300 uses a stock ICEPower module with only 10K input impedance. That is a good bit lower than what ARC designs into their amps. REsults may still be fine though on paper this is a less than ideal match.

I'd consider the Wyred 4 Sound amps as a cost effective alternatie to the S300. These also use IcePower but have additional input stages that raise input impedance to over 60K ohms to work better with a wide variety of tube pre-amps. Bel Canto does this also in their more expensive IcePower amps, like the ref000mkii.
Is it safe to say this would sound bright? How about a cary amp like the caa1?

Its hard to say what the sound will be like other than that distortion might be higher than otherwise. You'd have to hear it. There are many factors that contribute to the end sound It may in fact sound fine. Specs only provide a basis for comparison and do not tell the whole story alone.

I've never heard The Cary amp but it has 100K input impedance with rca connectors and 200K balanced. That is very good for use with a tube pre-amp! Not surprising in that Cary like ARC is heavily into tube gear so I would expect their newer SS amps are designed to work well with tube pre-amps.