I don't agree with your 1st statement in which you have done an audition of Polk Audio Rti A7 at the Pro Fx showroom, as I also own these speakers and they demand a lot of power to perform. In your statement you have mentioned that during the movie presentation the bass was good but during the music session these speakers lacked Bass performance. The AVR with which it was paired was Denon 3310 according to your post, now here I would like to make a point for all Polk (would be) owners and those even at ProFX that these speakers need descent amout of power from either an AVR or integrated amp and I have come to know about this the hard way:
Earlier I had a modest setup of Sr705 Onkyo and wharfedale tower based speakers, now the time came when I decided to just upgrade my speakers with Polk but during my auditioning I couldn't audition RTIA7 but it was RTIA5 which has just 1 tweeter and 1 mid woofer, I somehow liked the sound signature of these speakers during audition so I blindly ordered its step up model. The day came when I went to take the delivery of those speakers but I couldn't believe my eyes as with the packing on they were really huge speakers and even a car like Innova could not accomodate my entire 5.1 speakers from Polk so I had to let go of packing then and there and this helped me to a certian extent to accomodate my speakers. The disappointment came when I connected the entire series to my existing AVR i.e SR705 and it was sounding all right with movies and with the sub on, but when it came to music on pure direct mode the AVR could not provide the juice required by these huge speakers and the result was that as I increased the volume the AVR started to clip (meaning Bass was flatened out), then there was an option with this AVR to biamp the front speakers to which I decided to give a try and it worked this time. So my setup was running smoothly this time around but in my mind I knew that its running in a compromised fashion and I could get much more out of these speakers. Then I guess that God must have read my mind and I got a call from a dealer from whom I had bought those speakers that he has got a very good deal on a Nr905, and since the time I have incepted 905 in my setup I never looked back. The bass is tight and punchy, and for movies the sound is Wow. This reciever is so dynamic that even if you forget to turn on your sub, it doesn't let you feel its absence.
I am sorry for this long post but I wanted you to explain that for these speakers you really need power and that too in abandance. I would request you to go to pro fx showroom once again and ask them to connect these speakers with the Denon High end Pre and Power combo this time.Also while listining to music use Pure direct mode rather than the stereo mode as pure direct mode disables all the audissey and crossover settings of the AVR. Audition it once again as stated above and then update us.