audible illusions vs supratek, vs holoaudio vs backert

starting to re-build a system and thought I'd start with some well known budget pre-amps that are supposed to punch above their weight.  i will be playing rock cd's only through atma-sphere m60's.  speakers and cd player are still TBD.  any thoughts/comparisons on these brands.  Obviously the supratek and holo are cheaper, but still wouldn't mind some overall feedback as I have never listened to any of them.