Choice of Vandersteen models

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

My brother took me to Casa Guadalahara, if only I knew Stereo Unlimited was a few blocks away...
B

And, if you are like me, and want to save some cash, you can buy a pair of Treo's and 2wq subs and get 90% of a Quatro.
When I got the Treo's, I didn't realize that they share a similar footprint. But, now I realize that the Quatro is a bit deeper(due to the included sub) and it works better for me and my room- The subs can be moved to inconspicuous areas and still do their job.
I do know that John at Audioconnection has a pair of Quatro Wood's used, for sale. See the website.
B