IMHO, Squidboyw has offered the best advice so far. Given that you have NOT told us anything about what you have done to improve the sound thru you M804 speakers, we have to assume that you did nothing! Might be a very bad assumption but you gave us no choice so far!! :-) Please tell us about your room & its acoustics & what you have done to ellicit the best from the M804. Again, IMHO & being a former B&W owner, if B&W made a series of speakers worth owing then it was the Matrix series. It's that M801 sitting in George Lucas' studio that's B&W claim to fame. The Nautilus series speakers, in comparison, failed. IMHO! If were you, I optimize the setting before letting go of this gem. Or, finding a M801 as a replacement if you cannot optimize the M804. \
Most people buy & use audio gear as it is manuf in the factory rather than buying a good pedigree piece of gear & then modifying it for improved performance. Often, I have found that the performance of a good pedigree piece of gear, when modified or optimized in its setting, far exceeds the purchase of a new piece of "latest & greatest" gear.
Anyway, FWIW. IMHO.
Most people buy & use audio gear as it is manuf in the factory rather than buying a good pedigree piece of gear & then modifying it for improved performance. Often, I have found that the performance of a good pedigree piece of gear, when modified or optimized in its setting, far exceeds the purchase of a new piece of "latest & greatest" gear.
Anyway, FWIW. IMHO.