Also -- don't necessarily confuse "opamps" with "chips" opamps, after all, started with tubes in analog computers of the 1940s and 1950s. One one can buy monolithic transistor pairs etc. I even worked with a researcher once who had invented a solid state tube/ Really - a vacuum tube. It never when anywhere if anyone's interested.
In general, chips allow for complex designs that would be large and costly in discrete form. They also allow for decent device matching as a side product of the monolithic process. These are good things.
On the other hand the very geometry and small size leads to compromises, and things like connecting resistors etc. must, in reality, be semiconductors -- not metal film, carbon film, etc.
I also question whether all the complexity chips allow is good for the sound. Ok, i don't question it, I think its NOT.
In the end though, good design is good design. I've made differential front-end amps on a chip sound almost tube-like. Except they are quiet, have bass, and don't degrade.
By the way today's best opamps and instrumentation amps are vastly, vastly better than they were 20 years ago. One very well respected designer int he rockies uses them at the heart of a stupid-expensive preamp. And it sounds good: i've used the same device.
Happy thanksgiving. Everything soudns better after good wine and good food with good friends.
G