I owned the original Fontaine, so, not sure if my observations have any relevance.
They had the Dynaudio Esoteric tweeters which were divine. With the right amp, the bass was very tight and fast. The midrange was not quite as "present" and maybe a little polite compared to what i have since moved to... which is very efficient w low watt tube amps. But now I don't have the extreme ends.. which is typical, as you can't have everything w/out spending big bucks.
I think these punch very good in their price range. I found that the originals loved big power... maybe the Sigs are more efficient?? I switched amps around a bit and ended up w a 600 watt Mac amps, which were a crazy good combo and best bass i ever had. Lots of people liked the Class A Krell's w these as well... that is "back in the day."
If I had these, I would try to have a listen to a Class A Solid State. Maybe 100 watts or more. And pair it w a decent tube pre amp.