Mixing speakers, 6 and 8 ohm?

Hi All,

Is it possible to mix 8 ohm speakers with 6 ohm speakers in a home theater (5.1) set up, or will that do bizarre things to my receiver? I'm looking at Quad speakers (6 ohm) to mix with KEF speakers at 8 ohms.

Please advise.

Thanks as usual,
the rustler