I use the OCOS cable Rrog speaks of and while I never compared my 5.5m length to a short OCOS run all I can say is that the music sounds darn fine to me. If the cable is doing some thing wrong due to the long run I can't hear it. Same was true when I used 5.5m runs of Supra Ply 3/4 and Morrow Audio SP3.
As Riz1 wrote the biggest improvement in my system was getting everything including the amps from between the speakers. My rack and amps are on the side wall now. So the long speaker cable run was well worth it to me.
