You actually need two resistors, a 10k and a 1k. And you only tap off of one of the AR outputs, not both. You can use SPKR1 or SPKR2, doesn't matter. And tap off of the (-) side of the cap, NOT the (+) side.
Basically it's the picture in the link above, except SPEAKER OUT is the (-) side of one of those two large caps, and SPEAKER GND is the AR ground (GND).
A good place to do the mod (where I do it) is right behind the AR speaker connector, on the back side of the board. You can install the two resistors there, where the speaker and GND signals are, and you can tie them to an RCA cable for the output, which you can zip tie to the board elsewhere.