Wanting to build a monitor attenuator - What does it require?

Howdy fellas,

Regarding the skyline-high price of attenuators available, I'd like to build my own box.

What would I need if I wanted to build an attenuator that has two inputs (stereo), along with a two outputs (stereo again), including another out for the sub?

Mike

Mine is a 4 pole stepped switch for input selection, a 4 pole stepped switch for volume, and a 4 pole stepped switch for output. This handles a stereo, balanced signal.
The volume attenuator is the pricey part. Mine is a Goldpoint but you can make your own out of precision resistors and a ~24 position 4 pole switch.

I'd suggest having at least 4 output options in your design - you may want to add more speakers in the future.

I don't use a sub any more so I do not have a sub output, but I would like an insert w/ a disable switch for running a EQ at times. 
I would also like to add a mono switch to sum stereo to mono passively.