Vandersteen Model 2CE's: Should I upgrade?

I've owned these Vandersteen speakers since 1992 and they have sounded better and better as the rest of my system has improved.I've compared them to much more expensive B&W's and like mine better. I have a Bel Canto Evo 200.2 amp which is rated at 125 watts per channel and a Conrad Johnson PV12 tube preamp. I'm aware that the Model 2 has been improved since I bouhgt them and that there now is a Signature series. One dealer also told me that it would also sound better with a Vandersteen subwoofer. Is the sound that much better to justify these expenditures? What about upgrading to the Vandersteen Signature 3A? Is that a much better speaker and is worth making the jump?