Amarra runs off iTunes, iTunes must be running for Amarra.
BTW I have tried it with 3 systems, a low end one where I noticed improvment, a mid level and a high end one where there was no improvement!
Please note these are my findings with my systems, I am sure Amarra is good it just didn't always work for me.
So even if I don't have a Mac, I am not a surprise to find that people have different results with Amarra. In my opinion, there are way too many things going on in computer playback (whether it is MAC or PC) to have consistent and predictable results without each one of us trying the equipment/software on their own system.