I only use Remus. The other systems I hear, still keep that high pitch that's reminesent of smaller liter cars. The Remus gives a nice lower tone without resonation. I have on my 840 and love the pitch. It'll rid of that annoying 'chainsaw' sound on the M3 as well. I'm putting on my M5 at $ 585/side you can't go wrong ! They sell at bavarian auto.