I have 4,200 ft^3. I thought the 800v4 was real good...and it is. But the 800v4 with two 500v4 is so much better. smile

The best advice I can give you is if you want smooth bass throughout your room, go multiples. If all you care about is your main listening position, one is just fine.

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