[Rotmammoth]

Okay Thank you all

 

[senndroid]

They have it right. Bassheads won't be happy with the 595s, but the bass that's in the 595s will be tight, controlled, and dare I say crisp. 

 

[jasonb]

 
595 and 555 are almost identical. didn't see a headroom graph for the 595. so it looks like the 555 will have more bass than your current 448, and will have much better low end.

 

[Rotmammoth]

Alright thanks. I was thinking about selling the HD 448's.  I've owned them for pretty much 1 year and have kept them for in good condition for the most part.  Does anyone know how much I should sell them for. Amazon sells new ones for one hundred dollars.

 

[R-Audiohead]

Something worth noting - unless you've already pulled the trigger (which I am guessing is likely at this point)...
 
You mentioned that you're going to use them as portables?
 
I advise against this; these headphones do NOT isolate.  They are entirely open backed....everyone around you will hear your music and you will hear their conversations.
 
Killer desk phones for the price though - I'd even ditch the e5.  50 ohms is on the edge for needed the amp, but I have heard from a couple places the e5 colors the sound a bit.  I say get the cans and try them ampless - if you're not satisfied think about the e5.
 
If you want portables DON'T go 595.  I have suggestions for you if you're thinking portables.
 
I personally love my HD 448 as portables for the time being - good sound for 100$!  We'll see how long before I upgrade the mobile setup..