A good hard case like the Agent18 or Aluminum ones from ebay are useful - they'll keep your player from getting dents from drops and from getting crushed. I think Apple Store sells Agent18s in-store for around 20 bucks.
80mm to 120mm adapter: http://store.yahoo.com/svcompucycle/fa80120-blue.html
Just a piece of plastic...but it'll all depends on how much room it takes and if it'll get in the waye
Btw...how did the SeaSonicS12-500w fit into the Praetorian? I was thinking about the same combo, and heard...
Compusa has something like that too. Can't recall brand or name of the switchbox. Soundcard goes straight to the switchbox, and then you plug speakers and headphones into the switchbox. Press the button on the switchbox to alternate between phones/speakers. Was <$10 iirc.
Using Pocket Amp 2 by electric-avenues, I remember the e2c didn't improve noticeably but the HD212 seemed to. I think the 212s sounded a little less muffed in the midrange, but that's recalling from months ago. If you have the cash, Mister X makes beautiful amps but your current headphones are...