New op amps, good idea?

Crossover? How about a DAC? You have to give a model for us to have a clue?

I assume it is the Apogee DAX in your system photos. Seeing as from what I have read the crossover is at about 330 hz, I'd say there is a good chance of it being improved upon. That is if your technician knows how to do it properly. All op amps are not created equal. I do not know what it has in there. As for other things, power supplies have always been one of the most important parts of audio equipment. Anything that can be done there will be beneficial. Further more, as usual, any capacitors that have signal through them might ought to be looked at.

You may be better off buying a new one that is better all around... Bryston maybe.

Oops,I may be wrong in that the crossover is possibly at 70 hz.

Another option, and maybe the best would be to eliminate the crossover for the Diva, instead using a capacitor only on the input of the amp on the highs. The slope may be different than what is there, but should sound better if done properly. My 2 cents.

Something like an older ARC tube crossover works that way- you could try one of those, as they are relatively inexpensive.

While it is true that technology has improved today compared to 1991, I would have to say that biggest trend today is that things have become more digital - HD TV, HD radio, digital modulation schemes for cellphone over-the-air protocols, digital cameras, Blu-ray DVD players, etc, etc. I.E. there is more & more emphasis put on the digital signal processor (DSP) piece of silicon inside a lot of electronics.
In the meantime, human-beings' audio range is still 20Hz-20KHz. I have looked at Analog Devices', TI's & a few other companies' standard parts catalog. Many of their standard off-the-shelf part numbers are the same as they were 10+ years ago. In fact, many of these companies pride themselves on this part - an off-the-shelf opamp part designed 10+ years ago is still for sale today (because it was a damn good performing part them & remains a damn good performing part today) & is still bringing in revenue. I even know some of the engineers who designed these opamps - they are still designing in the industry not necessarily for that same company.
So, the point here is that it is very likely that it is not your opamp that needs replacement (it very well could & it would be easy to find a similar replacement if your tech looked in the catalog) but you could definitely do with a replacement or upgrade to
* the diode bridge rectifier - use of FREDs or Schottky diodes (the sound of both of these is very different & some people prefer Schottkys over FREDs)
* a change-out of the electrolytic capacitors - use modern day computer grade or audiophile grade caps.
* a change-out of the resistors - use Caddock, Vishay, PRP, Dale, etc brand resistors or the very expensive Tantalum kind that Audio Note UK uses
* Upgrade the internal hook-up wires
* damp the overall metal chassis by using Dynamat (asphalt-based) or Cascade (vinyl based) or you can use the less expensive vinyl based stuff from Partsexpress.com
* upgrade the RCA jacks to any brand that your favour - WBT, Cardas, etc, etc.
* Make sure that your tech uses audiophile grade solder such as Wondersolder or Cardas eutectic solder or something else.
* Make sure that your tech cleans the PC board - all these years could have generated a lot of copper oxidation.
* One other thing to do is for your tech to touch-up all the solder joints just to make sure that there are not old solder joints & no cold solder joints.

I think that once you do all of this, you should have a more transparent sounding x-over.