Pre-amps with seperate power supplies .....

It`s true different and better aren`t the same.Can many audio components be improved upon? Yes! Grannyring is right in that lots of part choices are compromises by the builder to control cost and stay within a certain price target.Certain higher quality capacitors,resistors,wire,etc. wouldn`t be cost effectively for the manufactuer but can easily be improved by the owners of these components.Look at the standard power cords components are shipped with for one example of cost cutting.Of course the range of "part quality" compromise varies from one builder/brand to another.

"I think they know what they're doing"
They know exactly what they're doing and part of this decision making
includes economic considerations (with some companies it isn't the
engineer's call to make). Even expensive components can be built with very

average part quality to stay within a pre determined budget target. The
builders working with these cost limitations are able to produce good
sounding and competitive products. Those components can be easily
elevated to very good and excellent levels with well chosen better parts.

It you're satisfied with the choices made in choosing parts then that's fine.
As Grannyring astutely pointed out, there's is often room for improvement
(sometimes significant) as an individual isn't hampered with the same cost
constraints for their specific audio system. As I noted before the issue of
part quality varies from one builder/ company to another. This is why many
companies will offer upgrade packages (better, caps, resistors,
transformers, tubes, wiring etc.). They recognize much better quality is
available but the cost puts it outside the price target of the standard level
components (for example V cap or ultra grade resistors options).

It's a personal choice and I believe options to improve/upgrade is a good
thing, your call.
Regards,

8000.00 USD for a component is no indication it uses the best parts available(it may or may not). The point to keep in mind is the option to upgrade is strictly an individual one.If you don`t believe in this concept then you don`t change parts,it really is that simple.A number of listeners have made substantial improvement it the sound quality of their audio components by installing better parts.Some have modified and have gotten worse results no doubt.Many have done modifications/upgrades and this resulted in noticeable improvements.It depends on the particular application.The basic /standard component can sound very good, yet this baseline level can be increased in many cases.
Regards,