You could connect a Nile in series to a Klipsch (in 4ohm mode) to make a 10ohm load on the front left/right channels.
The speakers will probably not play at the same volume, but it may not make a difference if you mean to play background music.
The manual doesn't list this as an option, and you may want to contact their support to verify, but you could also connect the 2 sections of the Klipsch speaker to make each a 16ohm speaker, and use Surr Back/Mult iZone terminals of the AVR.
Then you could use the Zone 2 volume to control how loud each pair plays.
The speakers will probably not play at the same volume, but it may not make a difference if you mean to play background music.
The manual doesn't list this as an option, and you may want to contact their support to verify, but you could also connect the 2 sections of the Klipsch speaker to make each a 16ohm speaker, and use Surr Back/Mult iZone terminals of the AVR.
Then you could use the Zone 2 volume to control how loud each pair plays.