Keep B&W N805, add HTM2, or get 805S?

I just found myself a set of trade-in N805 at B&W dealer and I got it with stands at almost $1000 less than a brand new B&W 805S (with stand)...

Now, I am looking for matching Centre (HTM2), and rears...

A few questions (50/50 HT/Music usage):

1. How much better is 805S over N805?
2. Is it worth the extra money?
3. If I am thinking of future, should I get the latest 805s for possible future upgrade to towers?
4. Can I match B&W XTC center with the N805?
5. How much sound quality I lose, if I go with XT2, XTC instead?

1. 33% better.
2. Depends on your bank account.
3. And use the 805s as rear speakers? Refer to #2.
4. Sure.
5. ?