[N0sferatu]

I've done some homework and found that my phone (Galaxy S2) will not let you easily override the DAC in the phone so I'm forced with analog out.  With that said, I want a bit more power available on hand but I want something small enough that I can keep both the amp and the phone (it's rather slim) in my pocket while say at the gym.  Any thoughts?  For the most part it'll be powering a pair of IEMs but if I go on vacation I want enough juice available to power my HD600s or my AH-D7000s. 
 
I don't really have a budget on this so I'm open to suggestions but on the flip side I don't want to be really spending more than $100-150 tops on something like this.  Thanks.

 

[ClieOS]

Here are a few option for ultr-portable: FiiO E6, digiZoid ZO2, iBasso T3, and T5.
 
E6 will be the cheapest and smallest. It is quite good sounding but not as good sounding as the other three. ZO2 has more power than E6 and the bass boosting function is great. T3 is even better sounding than the previous two, very transparent but it won't have the fun factor of the EQ (which both E6 and ZO2 have). iBasso T5 is a little over your budget (including shipping will put it around $180). But it is by far the best sounding of the four and feature BTL grounding, which is similar to active balanced ground. Neither of the four is designed to drive full size with high impedance and low sensitivity, but T5 is probably going to be a little better than the rest, followed by ZO2. If you can handle something biggest, then you will have more options.