Ekinox, Esker (RIP) and Fragments of Sentience (RIP) are my favorite. I uploaded Ekinox and FOS on the forum, just make a research.
Brume d'Automne (uploaded too) and Forteresse for their traditional sense of music are to be named.
I totally agree with D_L, it possess a unique sound.
But musically, I think that the best achievement is still the first CD of Sorcier des Glaces