To Vandersteen or not to Vandersteen

I think it would be a bit of a sideways step with the Decapo being a bit more neutral and the Vandy having a bit more low bass

Why not look into a good sub or pair of subs?

I had the 2 Sigs and now have Thiel 2.4s which are much more dynamic and present with a much more stable image. Good for you for choosing time and phase coherent designs!

find them cheap preferably Sig 3A's so you can play them and sell them if you don't like them. they like power and they like medium to large listening room. the best sweet spot distance is around 10' and same applies to apart.
to me the definition and resolution is perfect while bass is somewhat slow. they're best for large symphony orchestras. great with 60wpc+ tube amp or 100wpc+ solid state amp. In my past experience at Audioconnection of Verona NJ John Rutan was demoing them with Quicksilver M60, Rogue Magnum 88, Bryston 3b-st or Ayre(can't recall model). Please tell which amp you're going to use

The Vandersteen sound is rich, full-bodied, lush. All models in the line have the same somewhat dark and very lush fullness. all in the line play well at low volume. All are full range (even the 1c's). If you have bright electronics, the Steens will be great. If you have somewhat laid back electronics, the Steens can be somewhat dark sounding and, to some, too dark. But, if you like a smooth, rich, lush and laid back sound... you will love the Steens. If, on the other hand, great dynamic PRAT is your cup of tea --- well the Steens are not weak in this area (they are weak in no area) --- but PRAT is not a strength. If micro detail is desired... here too --- not a weakness but not a strength.

I love my Vandersteens. They do everything well and nothing great --- so some find the Steens "less than exciting" in a short listening session. But they are great to live with because they do everything well, never fatigue and never get in the way. They are a great value too.