More Power or use subwoofer to boost bass for music

One thing that usually isn’t taken into account is the fact that, regardless of power, placement or how great we think our hearing is, human hearing is Not equally sensitive to all frequencies at lower to moderate volumes. So if you are speaking of low bass down near 30Hz, you would have to be listening at a nominal volume of about 80db before the bass seemed adequately loud and for frequencies approaching 20Hz, the listening volume would have to be up near 100db (considerably louder than I care to listen, any more). On the high end, frequencies perceptively balance out at about 60db. Thus was the purpose of the old loud button on many of the vintage amps.
One advantage to a good, well integrated sub/subs, is the ability to boost the bass volume to accommodate listening at moderate volume levels, without loosing the bottom end bass. It could be that you were listening to the music, at the dealer, at a louder level than it seemed. Not to take away from the other suggestions, but just another case for a good, well integrated sub/subs...Jim

That's Fletcher Munson equal loudness curves you're talking about. Duke has said pretty much the same thing. One consequence of this is its important when setting sub levels to do it at a level you care most about. 

I use matched amps and pre-amps for my older 803's and subs. This gives me control of the bass without creating out of phase signals. It also allows me to tailor the bass for the recording.  Many old albums really open up when the bass is not relegated to a recording mixed for what a 1960's 35 wpc amp could produce, or a modern AVR receiver.  Powered subs with frequency roll off controls, as well as tone controls, alter the phasing, thus negating B&W's primary design philosophy.  They are also hard to adjust for each recording. 

Also, you might want to use your amp for the subs, then get a less powerful amp for the 804's, if price is a consideration.  100 watts will easily power them, as long as you are using subs.

danvignau:”I use matched amps and pre-amps for my older 803's and subs. This gives me control of the bass without creating out of phase signals. It also allows me to tailor the bass for the recording. “

     If your tailoring the bass for individual recordings, that indicates to me the subs are are either not positioned properly in relation to the listen seat or the primary controls on one or more subs, volume, crossover frequency and phase, are not properly set.  Setting these 3 primary controls properly on each sub is very important for seamlessly integrating subs into a system and room, just as important as properly locating each sub in the room in relation to the listening seat.       It’s also usually the most time consuming step When incorporating subs into the system and room.  This is due to the reality that a good sampling of musical tracks, of different genres and containing significant bass content, need to be played to determine the optimum settings on these controls that provides the most natural sounding bass.
     If adequate time is not devoted to thoroughly completing this step and arriving at the optimum balance of bass settings for all subs that sounds very good on all music genres listened to, individuals may feel a need to adjust these settings prior to or even during playback.  Who would willingly accept doing that?

Tim