I don't know what the HD449 is like, but it will not be in the same league as teh other two cans. The comfort is pretty similar between the two cans so it's mainly personal preference. The DT770 will have more bass, but it is a bit boomy, with an amp it will get a bit tighter. The HD558 will have a more balanced bass that will come forward when amped. Both are great cans, but very different. The HD558 is a pretty friendly sound that will make most music sound good even it it was mastered poorly. The DT770 has a "fun" sound with more emphasis on the bass and treble. Either can may work for you, but the best thing would be to see if you can try out at least one. While this might not be possible, it would at least let you see if the one(s) you try feel and sound the way you want.
Thanks for the advice. As long as the bass on the HD 558 is still good, and by that I mean "accurate" then I'm pretty sure I will be fine as my music already puts bass above everything else. I have read on here at least twice that too much bass can lead to "fatigued listening sessions" or something like that. And I am starting to think that in addition to my headphones already being uncomfortable, maybe the added bass isn't helping...
So with that in mind, I am starting to lean towards the 558s. The only thing that I am worried about is that they are open and will have sound leakage. As far as I know, the 449s are closed which I have also heard can lead to more bass. And if they are in the same category when it comes to comfort, I am stuck between those two.
And I totally agree, trying them out somewhere would be ideal. Do you know of a common retail store that might have them?