A local car stereo dealer is recommending it. For those who don't know it takes the plug from the head unit, flattens the curve and allows for RCA's to a amp.

 

Unixgal had a professional system put in her MC and I believe they used a Cleansweep. She got JL speakers. Not sure about the Cleansweep. You might PM her.

 

Thanks Robin. I was think of you when I posted this. It might resolve your rear speaker frequency problems although you would need a different amp

 

I had one in my last car. I was more than happy with it and JL stands behind their product. I'm not sure of the efficacy of using it in the R56 with OEM parts, but you could easily build a system from it if you tapped straight into the OEM head and bypassed everything else.

I won 'Best Sound System' with my last car at several car shows....I think that says a lot about the SQ ability of the CleanSweep.