Choice of Vandersteen models

You may want to check the Audio Connection website. I think they had at least one of the speakers you're considering used. Having had the 5A's in a room that was 23' X 12', my guess is your room size should be a factor in your decision. 

I'm pretty sure the Quatro Wood will have the "tri-woven" midrange driver. If the model 5 pre-dates that driver, the decision should be much easier for you! Then again, the model 5 can be upgraded to 5 Carbon.

Also consider whether you will able to take advantage of the Vandersteen upgrade program; the 5s can be upgraded all the way to 5A Carbons.  I'm not sure if there is an upgrade program for the Quatro.  Worth checking with a Vandersteen dealer.

I think the upgrade program is for original owners, but going through someone like John Rutan at Audioconnection might grease the wheels...
As for your original question,
It depends upon how large your room is. I own the Treo’s (non CT), and they work perfectly in my 20x18 room-even in non traditional positioning.
I would expect the Quatro’s to work as well in the same space.
The 5’s might overwhelm a room that size. Once again, Johnny would be the best person to give advice on that subject.
As far as ’holding value’ goes, once a newer model comes out the older one drops. In my opinion, I think the Quatro to be the best in terms or resale ability, and the easiest to work with in a wide range of rooms.
B

I would go with Quattro's if your just comparing them to a Model 5. But you should seriously get yourself a 5A if buying new or from a local retailer. You may be able to get a demo pair for a decent price.