adding 2 channel amp to a 7.1 system

[Gman51]

can add a 2 channel amp to my 7.1 receiver to add two speakers

 

[jsmithepa]

Only if PRE-OUTS are available on receiver.

 

[americanaudiophile]

You can connect a speaker to line level converter that will provide a connection for the amp.
https://www.crutchfield.com/p_142LOC80/Scosche-LOC80.html
You won't be getting 9.1 channels just more power to drive additional speakers with two of the 7 channels.