I've been looking at the more expensive Boostaroo headphone amp to further boost line-in sensitivity on some of my boomboxes.However when investigating the website,I noticed that this high fidelity version also applies crossfeeding to the sound.This is supposed to blur or fuse part of the stereo channels together somewhat to reduce the risk of headaches when listening through headphones.As I am thinking of putting one of these between my Ipod and my boxes line-in,will this crossfeeding noticeably degrade the perceived stereo separation?Here is a link to the item in question:
http://www.boostaroo.com/store_detail.php4?id=13

From what I understand, these boost devices will not give you a noticeable change...depending on the music. I have heard of some shadowing. This is where, for example, your are listening to classical where you have a lot of strings,bells, chimes,cymbals and such. Slight blending will allow you to hear say, a tone that you'd only hear on the right, slightly on the left. But if you aren't paying attention you may miss it.

As far as headaches, this is only in a small fraction of listeners and usually results from compression of phones against the head or poorly fitting earbuds (which have their own issues), or excessive volumes and irritable distortion. So for these small few an amp may make a difference if the headache is audio related.

Boosting amplifiers will definitely give you better audio clarity and though I have not listened through a Boostaroo personnally I know some who swear by them.