Amorphis

For their earlier sound, I'd recommend Tales of a Thousand Lakes. Try to get the edition with the hilarious cover to Light My Fire.
 
You should definitely check them out, they're very good. They're most famous for combining folk music with metal, but they've strayed pretty far from that sound at times. When I was first getting into the more underground metal back in 2000 or so, there were 4 main bands that everyone I dealt with recommended - Opeth, Katatonia, Amorphis and Anathema. I still kind of consider them to be closely related in career length and sustained quality over time, though Amorphis is a bit less consistent than the others.

Elegy and Tuonela are the best, imo. Tales from the Thousand Lakes hasn't aged nearly as well. The clean vocals on that one also sound like an elf with a pole up his ass. the "My Kantele" ep is also incredibly awesome, if you can find it. 'Am Universum' is pretty good but not really that much like the previous two and more hard rock than anything, 'Far from the Sun' or whatever is totally lame, and the new one is surprisingly pretty damn good and sounds like a bridge between elegy and tuonela.

In conclusion - get Elegy then Tuonela then Eclipse. Tales from the Thousand Lakes is historically relevant but I don't find it particularly enjoyable. And that cover of Light my Fire is intolerable (though hilarious for the first minute or so until you realize they're going to do THE WHOLE SONG).
 
I really don't understand all the hate that the new album is getting at all. If anything it sounds like a step back in the right direction after a few lackluster albums to me. Though I'd still just start with the old stuff. Mainly Tales From The Thousand Lakes, Elegy and Tuonela, and possibly The Karelian Isthmus if you want their more basic death metal sound.
 
I really don't understand all the hate that the new album is getting at all. If anything it sounds like a step back in the right direction after a few lackluster albums to me. Though I'd still just start with the old stuff. Mainly Tales From The Thousand Lakes, Elegy and Tuonela, and possibly The Karelian Isthmus if you want their more basic death metal sound.

This is the first negative reaction to it I've seen, actually. Not that I've seen many reactions to it at all. It really does sound like it could fit between elegy and tuonela comfortably to me, and the new singer isn't half bad either (hardly any worse than Pasi at least :P).
 
nostaliga metal really. not breathtaking...but enjoyable on a similar level to early katatonia and paradise lost.

No, it's plenty breathtaking - one of the first really classically influenced death metal albums - and one of the best. It beats the hell out of the sentimental crap you mentioned, and it's not all that similar even at a reductive level.