Best means of isolating digital equipment i.e. DACs, CD transports, wall warts etc.

Is it better to route these digital noise polluters through a conditioner, isolation transformer or both in series?  Is a "digital" power cord sufficient by itself or could it be used with any of the above without negative side effects?  There are a lot of anecdotal observations in many old threads.  Can anyone help clarify based on what they have found?  I'm getting ready to add a dedicated circuit for my audio system and will be reconfiguring power cable connections.