Looking to upgrade my Sennheiser HD-280s..

Hello.

I've had my HD-280s for years and now I'm looking to upgrade them as a Christmas present to myself.

I mainly listen to music through my iPod without an amp. I've heard it's not best to use higher end headphones with an iPod, but I listen to most of my music away from a computer. 

So, my questions are..

1) What do you recommend I upgrade to? I'm looking for something in the $200, maybe $300 range. Also, I mainly listen to rock music.

2) Could someone explain the aforementioned iPod issue to me? Would an amp fix it?

Thanks!

I would prefer closed headphones. And define portable? I thought all headphones were portable? Sorry, I'm just not completely savvy when it comes to audio.

And thanks. This topic was the reason I registered an account lol

Portable in the sense that I'd look dorky wearing them out in public? Lol that's fine. I usually use them in my room and on car trips.

One thing I disliked about the HD-280s were the cuffs, there were kind of small around my ears and they would hurt after prolonged periods of use.

The HD-25 I-IIs look like they'd be murder on. 

Hmm..

The Amazon reviews on the Aiaiai (how you pronounce that? aye aye aye?) say that these require EQ and the iPod doesn't have an equalizer.  I think I might need bigger cups than the ones your recommended. They ARE supposed to go over the ear, right?

People talk a lot of about the ATH-M50s...will these have a much higher sound quality than my HD-280s? Would you recommend those or is something better? 

After doing some research I was thinking about getting the Beyerdynamic DT 770-PRO 250 ohms with the FiiO E11 amp. Would the E11 have enough power for the 250 ohms?

Any reason that would not be a good upgrade for me?