Empiricism...I think this is the most well done album all around, also it has the best production quality and Vintersorg on vocals.
Quintessence would be my 2nreccomendation because there are some really great songs on there, especially Colossus.
and finally Epic would be my 3rd because its like Empiricism but with more colors and melodies, plus the guitar tones are raw and righteous.
Most likely you'll be able to find Epic, Empricism and Quintessence in stores because they are the most recent. You might have to look online for the rest, like The Olden Domain, Archaic Course, and the self titled album.