Can we really expect a simple pre amp to improve on the mastering engineers ear and gear? If so just put a bunch of your favorite preamps in series and the sound would just keep getting better!Improve on it no- maintain neutrality yes.
If you were instead to put a bunch of your favorite passive volume controls in series, the result would not be pretty. Nor would putting a bunch of active preamps in series. The idea in high end audio is to do the least damage to the signal while getting it from the source to the speakers.
The simple fact is that a passive is too simple to do the job. The reasons why have been explained several times in this thread.