Original Vandersteen Model 3

I doubt that RV would want or be able to upgrade a pair of older 3s to current spec.  Almost every aspect of the 3s has been changed over time as all of RV's speakers are of an evolutionary nature.  If he could do it, it would no doubt cost more than simply buying a new pair of 3A Signatures.  If you get the chance to listen through the Model 3s that are available and are satisfied with their sound then the price you're talking about seems quite reasonable.  Having owned an early pair of 3s, I found their main weakness to be a bright treble leading to a bit of glare in the upper midrange.  If you are using "warmer" sounding components it could make for a happy marriage.

I owned the Vandersteen 3A's for years and they were sweet, warm and musical but with sluggish bass, no matter the amp, of which I tried quite a few.  I upgraded them to 3A Sig status (which only the original owner can do) and they're way better.  Actually decent with the additional bracing in the cabinet, upgraded crossover and new mid/tweet drivers.  I would not, could not own the 3A again.  The 3A was reviewed as a major improvement over the 3.  I've seen a few 3A's advertised for $800.  $500 for a 3 is probably fair market but no big deal.  

I also did not like vandy's because they're slow. They're great for orchestral music, but for small bands, rock and electronic instrumental music they don't do the trick.
The best Vandy combo you can get is by purchasing 2x 2WQ subs with 1C smallest floor speakers. 2WQ bass is substantially faster than in any integrated speaker they've ever built.

I had a pair at one time and found them to be quite good with excellent imaging.

I think Vandersteen offers upgrades for the 3's, but it isn't cheap.
For the price, I don't think you will be disappointed, but if you think you will be looking for 'the best', I would suggest either waiting for the 3a sigs or better yet, a pair of Treo's or Quatro's.
True, they are more expensive, but I though I was never going to have 'upgraditis', and ended up selling my 3a sigs and getting Treo's. I should have listened to Mr V. and just gotten a pair of Quatro's and been done with it.
Incorporating a sub (or a pair) is one of the best upgrades for the 1,2, or 3's.
Bob