Dear Shakeydeal: I don't want to disturb you on the subject and my thoughts are in the attitude to give what IMHO is a worth to try alternative.
IMHO and due to my subs experiences the primary/main use of subwoofers in a stereo audio system ( not HT. ) is not to attain a best bass response but to lower the IMD in the main speakers ( almost any passive speaker. ), let me explain:
if we take your P-10's and due to its woofer crossover frequency point ( 500 hz. ) " we " are asking to that woofers ( drivers ) to reproduce with accuracy at the same time frequencies that its needs are different: 30 hz , 100 hz, 200 hz, 500 hz and the like, those long woofer excursions of a 30 hz frequency " disturb " and degrade the quality response that that same woofer has to reproduce on higher frequency range ( say 100 to 600 hz. ), this kind of interrelationship between different frequencies that most be reproduce by the same woofer/driver has a name: Intermodulation Distortion. It does not matters how good the woofers and design are that IMD exist and degrade the quality performance always ( nothing is perfect and exist trade-offs. )
What happen if we liberate that woofers from 80Hz and down ( that the woofers in the main speakers handle only the range from 80 hz and up )?
the IMD goes at minimum/lower given you a better/clear midbass/upper midbass/lower midrange, and not only in the original woofer frequency range but " clean " all the main speaker performance where you now can have and will hear " sounds " that that IMD hiden before: now the main mid range and high frequencies are outstanding with a presence that you never before attain in your system.
with the integration of two subwoofers in true stereo way you will have additonal benefits: not only a deepest bass but a more accurate bass because this frequency range is now handle by a dedicate woofers that were designed in specific for that frequency range and where too the subwoofer dedicated amplifier was designed in specific for that critical frequency range.
other advantage is that your main amplifiers will work a lot better because now the frequency range operation is from 80hz and up.
now you don't have to made/make any compromise in the room placement of your speakers between the " best " bass against the " best " midrange/high frequency/soundstage. Now you can choose the best place ( room interaction ) for your main speakers and the best place ( subs ) to attain the whole quality audio system performance that you and the music deserve.
Only an opinion.
Regards and enjoy the music,
Raul.
