Thanks to everyone for taking the time to give me advice! Just FYI, I have an Accuphase DP75V CDP, a ML 32 pre, an Edge NL12 amp, & Cardas Golden Ref IC & spkr cables. Some have advised me to switch to Piega C3, but I will try to heal the current problem with some of your suggestions.
I spoke to someone at REL who also suggested room treatment before using a sub.
I was curious if people had used a sub in any situation to replace the speaker's bass performance rather that just extend its range.
By the way, the reason I am really trying to keep the P10s is that they seem to have perfect tonality on just about every musical component, even difficult ones like voices, trumpets & other brass, piano, cymbals, and electric guitar. Nothing is too brash or too dull, but just right, Goldilocks-like. Plus they have satisfying depth & width, and create rounded, distinct images, not thin but not bloated, either. I used to have Wilson Watt Puppy 6s (great bass, but artificial, almost unlistenable portrayal of voices on many recordings), Arial 10ts (nice tonality, but shrunken, flat images), and Apogee Stages (natural, live sound, but compressed on orchesteral music and unreliable with unfixable woofer buzz in one speaker). (I'm just a listener with no connection at all with any audio company.) Thanks for reading and any more feedback is welcome.