highpass passive line level crossover pllxo design

I am looking for information on the design of a very simple passive line level crossover for bi-amping an old set of maggie tympani iii. I have found two different first-order RC filter designs, and wonder if they work equally well. They appear at:

http://www.silcom.com/~aludwig/Sysdes/RCfilter_circuit.gif
and
http://www.t-linespeakers.org/tech/filters/passiveHLxo.html

The difference is that the resistor is in series before the capacitor in the latter and in parallel with the amp following the capacitor in the former. Can anyone explain the different effects of these two simple circuits?
thanks