[MerlinWerks]

You could try a Shunt Mode attenuator, only one high quality resistor in the signal path!

[Occam]

As its a voltage divider, whatever isn't shunted down to ground, goes to the divider's output, wouldn't you consider the that shunt resistor(s) in the signal path? I'm not asserting its as important as the series resistor, but does the shunt have a significant impact?

Regards,
Paul

[JoshK]

The way I look at it, the shunt resistor is in parrallel with the load, so it divides the AC current loop.  In other words, it is in the signal path. 

[Mike B.]

here is a more detailed discussion on the Ayre

http://db.audioasylum.com/cgi/m.mpl?forum=general&n=529196&highlight=Charles+Hansen&r=

[MerlinWerks]

As its a voltage divider, whatever isn't shunted down to ground, goes to the divider's output, wouldn't you consider the that shunt resistor(s) in the signal path? I'm not asserting its as important as the series resistor, but does the shunt have a significant impact?

The way I look at it, the shunt resistor is in parrallel with the load, so it divides the AC current loop.  In other words, it is in the signal path.

Of course you both are right wrt the shunt being in the signal path, it became clear to me after redrawing it 
I guess if you built the actual S5 attenuator you would only have two resistors in the path