I have a 3G Touch which I connect directly to a set of Westone UM3x. I'd like to be able to adjust for both tone and balance in the channels, and of course the limited eq presets on the 3G are, well, limited. Searched for an app that could provide these features to no avail, so I'm thinking I need some kind of portable headphone amp/mixer that might do the trick.

Any suggestions would be welcome. Budget less important than getting the right features and sound quality.

Thanks.