Great, I lost my post when trying to send it. Let's try this again.
As we know, there's no such thing as overkill
But aside from that what benefit would a 600 have over two 350's or in this case a HSU and a 350? The ability to go slightly lower, any other?
My speakers will be with me longer than I will be in this house (most likely). We have our second on the way, due in April, and we've been talking about moving for a couple of years. It wasn't needed before, but now time will tell. It's a lot easier to buy the sub now then it will be later...this is more of an excuse
I'm very happy with the Hsu and don't feel I'm missing much but I do have some nulls in my room. The room opens at the front right to a hallway and an office (you can see behind the equipment rack). I've recently taken the sectional apart and made two rows of seating. In doing so, I moved the Hsu to the front of the couch on the right side (if facing the system). It appears to have more even bass in this spot and is a convenient end table/ottoman. However, I don't like my guests using it as such and it's not esthetically the best place for it. I'm sure the wife, no matter how easy going, will ask the room be changed back soon as well.
If the consensus is to leave the sub as is and pick up the QS or to move to vertical center (JohnK) then that is fine but for some reason I seem stuck on bass for the moment.
