I agree!
As long as your Adcom is working properly, there is no real advantage to buying a newer amp.
Power amp technology was pretty much mature well before the GFA7000 came out and Adcom is solid gear! (there have been innovations, but none of them threaten a good solid class AB amp like the Adcom for SQ).
Speaker technologies have improved since yours were made (I am not personally familiar with VPMS speakers).
A very good speaker from the 90's is still a very good speaker today, but the equivalent Sound Quality is generally available for less money in today's market (inflation adjusted).
The subwoofer is where a change would most likely yield improvements. A great sub from the 90's is still good, but where it really falls flat is in the ability to tune it to the constraints of your room. If you happen to have a great fit between your room and the sub (which could best be evaluated with measurements), then you are gold, but more likely there are opportunities for improved SQ (sound quality) if you add some tuning options.
If you just really like the idea of the brand-matched VPMS sub and speakers, adding another "Tall Boy" sub is a great option. Here is an article explaining the benefits of dual subwoofers (showing FR charts without getting too deep into the technical details - if you want technical details, let us know and we can give you more links!):
We discuss the benefits of multiple subwoofers by comparing measured performance of two subs vs one. We discuss using two smaller subs instead of one larger one to provide better bass for all seats.
www.audioholics.com
Understand that many of us have upgraded amps like you are proposing, and while on "the day of the wedding" we may have convinced ourselves that the new gear sounded better, a revisit of the old amp after the honeymoon was over revealed that there was no appreciable difference!
That is why I am suggesting you look at subwoofers (and, to a lesser extent, speakers). You will hear a difference and the difference will have staying power after the "honeymoon"!