Hi,
If you are looking for an amp, I would suggest getting a decent desktop one, as it will significantly outperform most portables. However, if you are dead set on it being portable, there are a few nice possibilities. The cMoyBB from JDS Labs is one of the nicer cMoys. Another option is the PA2V2 for around $60, and the E11 as you mentioned.
I don't completely agree with this author, but he has a nice article to start with. http://www.headfonia.com/music-on-a-budget-sub-100-portable-amps-shootout/
Then there's this hyped up Objective2 amp that has been getting a lot of good attention. It's battery powered, but it's size makes it slightly more suitable for sitting in your backpack rather than your pocket. It's creator is banned from this forum, but he claims that his amp outperforms many highly-regarded portable amps such as the Headroom Micro, as well as the SRA SR-71B. I can't vouch for that, but I will say it sounds very nice for its price, about $150 assembled, or $50 if you DIY like me. :)
Hope this helps!
-Tony