System tuning tips from Hi Fi Plus

The folks from Hi Fi Plus put on a system-tuning seminar at RMAF. Their recommendations included: (1) use cables from only one family in your system, (2) get a non-resonant, non-ferrous component rack, and (3) clean your cd's....They had equipment problems during the session of the seminar I attended, so I didn't get to judge the actual improvements gained by these tweaks, but I'm interested in just how important/helpful you all have found these suggestions to be...