I am now regretting buying the Mixamp 5.8 due to possibility of hissing. I imagine this will drive me up the wall more than anything else. I should have bought a wired amp, but I didn't know enough at the time to be wary of it. I need to take a break from reading all this stuff.
Take a deep breath . Reading all of this stuff really can drive you crazy.
Like chicolom said, I doubt you will notice any hissing with the Mixamp 5.8. I Love mine...no regrets at all.