I have no hiss problems with my Livewires connected direct to ipod or iRiver - nor through my RSA Tomahawk, iBasso D1, Meier Headsix, Headstage Lyrix, or my PenguinAmp Caffeine when set for low gain. My PenguinAmp Royal has no gain switch but is pretty quiet.
If I kick up the gain on any of the amps from low gain to high gain (which is for full cans or high impedance cans, not IEM), then sure, you will hear some hiss coming from the ipod being amplified.
My $40 JSeaber cmoy bass boost amp is always at a relatively high gain (only slightly less high with an optional gain switch installed). Having no volume control it will amplify the ipod hiss fully, even with ipod volume low. The Shure volume attentuator can take off a great deal of hiss, and still allow that amp to play loudly if you turn the ipod volume all the way up.
Earpeace aka Livewires will be offering a 50ohm inline resistor that reportedly improves the sound (which is already excellent) and lowers the tendency to hiss with higher gain levels.