Combining a stereo pair and single in same group

Hi.

I'm sure this has been asked before but I haven't had any luck finding it in the forums.

I live in a small apartment and have a 3 in the bedroom and a 5 in a lounge. Love the full sound this setup gives me throughout the place but starting to really miss stereo separation.

If I get another 5, can I set it up as a stereo pair with the other 5 and still have the single 3 in the same group as the stereo pair?