Well I'm looking for bascially what is fitted to the empeg harness. It is a filter and fuse holder combined. Pretty much every head unit you see has something along these lines. My Alpine HU has a separate 3AG fuse holder and a power filter which is basically a 1 winding transformer to give a large amount of inductance. I don't have a spec other than it must be able to handle up to 3A given that's what the standard fuse is.

I don't mind having the fuseholder separate to the filter, but I can't even find the filters. Autoleads supplied the original empeg one, but I can't find it on their website and they only seem interested in Europe.