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

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,

Most manufactures of high priced equipment do not include a “named” audiophile approved power cord for the simple fact that buyers in the price bracket want the flexibility of choosing their own audiophile approved PC. It analogous to why hi-end speaker companies do not include speaker cables with their products.

I have not read all the responses but will agree that just because a product has a separate power supply does not make it better. It all comes down to the design. You can put a crappy design in a separate enclosure just as easily as a superior design.
We do it in our Purity products due to space restrictions. There is no way we are fitting a dual mono PS and all the analog circuitry into a single chassis.

I also agree that umbilical cords 'can' make a big difference but just changing one out does not guarantee better performance. You have to take into consideration wire gauges that can alter voltages if differences are too large.

Charles1dad, True

"It analogous to why hi-end speaker companies do not include speaker cables with their products."

Speaker cables may not be included, but some speaker manufacturers offer their own brand of speaker cables. Naim, Dunlavy, ProAc to name a few. A little company called Hammer Dynamics also had very specific speaker cable to match their speakers and it just so happens nothing works better.