First of all what 65 what amp are you using? If it is for example, a Levinson #29 or a Krell KSA 50 then you are getting much closer to 100watts (or maybe closer to 130) into the 3A’s 4-ohm load (a bit lower in the upper base). I you are using a less substantial amp then the wattage may be an issue.
For a time I used a Creek 4330 integrated on my 3A’s (45 watts or so, maybe 70 or 80 into the Vandies load). It worked fine, somewhat limited as far as dynamics, and caution was used at high volume levels. That said I think you will find that the Vandie 3A and the Signature model perform better with at least a 100 into 8 ohm and a 200 into 4 ohm amp. This implies a stiff power supply, and the ability to deliver current. Some recommendations: McCormack DNA 0.5, McCormack 125, Belles 150A regular or Hotrod (a great match). Tube amp wise there are less low cost choices, but you can get by with 60 tube watts.
Regarding the upgrade to the speakers. I personally recommend it. The tweeter opens up the 3’s high-end a fair amount. This contributes to a larger soundstage, and more defined imaging. Some might say that the Sig. Version has a less vandie sound i.e.: less dark. I do not agree with the “dark” description that Vandie’s get. I think the others are generally on the bright/aggressive side of natural.
To answer the question for me, the $750 upgrade was worth it, I upgraded my 3A’s to the signature model. The difference is significant (but subtle), and the improvement you will hear is dependent on the quality of the rest of your system. The other thing is the difference (to me) is 95% related to the tweeter change, a more powerful amp may effect the high end, but will more likely impact the bass range. So that is where what is important to YOU in the sound comes in. Good luck.
For a time I used a Creek 4330 integrated on my 3A’s (45 watts or so, maybe 70 or 80 into the Vandies load). It worked fine, somewhat limited as far as dynamics, and caution was used at high volume levels. That said I think you will find that the Vandie 3A and the Signature model perform better with at least a 100 into 8 ohm and a 200 into 4 ohm amp. This implies a stiff power supply, and the ability to deliver current. Some recommendations: McCormack DNA 0.5, McCormack 125, Belles 150A regular or Hotrod (a great match). Tube amp wise there are less low cost choices, but you can get by with 60 tube watts.
Regarding the upgrade to the speakers. I personally recommend it. The tweeter opens up the 3’s high-end a fair amount. This contributes to a larger soundstage, and more defined imaging. Some might say that the Sig. Version has a less vandie sound i.e.: less dark. I do not agree with the “dark” description that Vandie’s get. I think the others are generally on the bright/aggressive side of natural.
To answer the question for me, the $750 upgrade was worth it, I upgraded my 3A’s to the signature model. The difference is significant (but subtle), and the improvement you will hear is dependent on the quality of the rest of your system. The other thing is the difference (to me) is 95% related to the tweeter change, a more powerful amp may effect the high end, but will more likely impact the bass range. So that is where what is important to YOU in the sound comes in. Good luck.