I don't recommend rear-mounted. Our ears are rather insensitive to sounds from behind. I've tried QS8s, QS10s and M3s behind me all with poor results.

I lived with QS8v2 for 12 years and I am very, very glad I switched to QS10s for the sides. My QS10s are located 10' away from me and they are great performers.

Also I lived with a VP150v2 for 11 years. The VP160v4 is far, far better.

I am very surprised with how much I was missing with my v2 compared to the v4.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated