Triptykon are cool, I listened to them back when the tracks were first put up on the myspace. It's much like I'd expect Celtic Frost's next album after Monotheist to sound like...
As for Opeth, I'd recommend all the albums from My Arms, Your Hearse onwards. Not that I dislike the first and second album, it's just I think they really came into their own on My Arms, Your Hearse - and haven't really stopped progressing since.
Triptykon isn't exactly new