I haven't gotten to listen to ALL of the bands yet that were suggested. But so far the only band I have liked the sound of is Monokromia. I've also known about Novembre for a while but his voice is nowhere near as good as Jonas. However I would place them at second place behind Monokromia. I already know of Opeth (too much growling), Anathema (too slow), Paradise Lost (not a big fan of the vocalist) and My Dying Bride (again, I don't like the vocalist). I really don't like any of those bands and mostly it's because I don't like the vocals. In my opinion vocals can make or break a band. So far the closest band I can come to to Katatonia is like Tool/A Perfect Circle. It's all about the vocals for me. So if anyone knows of other bands who sound similar to recent Jonas material (with little to no growling and lots of malisma vocal techniques) please tell me about them and I will definitely check them out. It doesn't even have to be rock. I even love Gregorian monk chants to just because I love the melodies in their voices and thats also what I like about the more recent Jonas stuff.
Jack