Watt size resistors should I use in an L-Pad circuit?

[acidbasement]

So, I want to build an L-Pad based headphone adapter so I can connect headphones to the speaker outputs of an amp. This is mainly for S&Gs, but if it works great then I have the added bonus of having my innate and poverty-enhanced cheapness vindicated.

I was planning to use this information from Meier to optimize the impedance for my headphones: http://www.meier-audio.homepage.t-online.de/ - click on "tips and tricks" and look under the impedance optimization title.

One thing I can't figure out (yes, I'm challenged with these types of calculations) is how many watts the resistors should need to be able to disspate. Let's assume I have an amp that maxes out around 50W into 8 ohms. Anyone?

[acidbasement]

Uh, I guess I'll just use some big ones and see how hot they get then.

[Mister X]

Headphone Adaptor for Power Amplifiers

[acidbasement]

Beauty, thanks! That spells it out about as simply as possible.