I'm glad to hear you added a sub. Even an old, cheap sub is better than no sub with your M60s in that big room. I lived with a cheap Sony sub I bought at London Drugs for 100 bucks for 11 years. Still rockin' with my Audiobytes.

It's difficult to say if you need twins. Dual 600v4 are not as great in my room as a single 800. Neither are quadruple 500v4. The 800 ought to get more love than it does in this industry.

An 800v4 with M2v4 is a damned good end game!

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