To expound on GAD's post: Romanee on this forum has found little if any difference between the TH and Hornet after 500+ hrs of playing. My Tomahawk had about 500 hrs and noticed NO difference between it and my previously-owned Hornet, sound-wise.
I used both Hornet and TH to power Ety IEMs, Beyer 880 and 990, both 250 ohms, thru an Imod and everything sounded wonderful.
Bottom line: I'd have no hesitation recommending either amp for both IEMs and larger headphones. Or get both--use the Hornet for a larger player like the Ipod or similar and the Tomahawk for the Nano, esp the new 3rg gen which is almost a perfect dimensional match for the new Nanos