My airplane has no extra soundproofing at all-- just what it had from the factory, including the tuning forks.
I've had experience both ways. While the soundproofing does make a difference, in my opinion it's not enough. And, I wanted the extra useful load. So, I put in a 6-place intercom and bought 6 noise cancelling headsets. Everyone wears a headset, and they are all happy-- and if they want to listen to music or watch a movie in the back, they are all set up for it.
A quieter cabin is another advantage of a 1000, but I'd still probably do the headset thing.
My airplane weighs about 6950 pounds with full interior, and with the Keith Freon system (plus the Sundstrand).
Corvallis is about 75 miles down I-5 from where I am. It's a nice city.