Hi
Tell ProFx to give you the RTI A1s for 17k......yes the cone material of the speaker, the cabinet type etc and also the quality of components used in the cross over network....that's what makes it better and more refined.
Product- PROFX
Both speakers seem more or less same in looks, there is a difference!
The AVR is on the higher side....he should ideally give it for 43k types as that is the rate and Denon has launched the X1300 which will be out shortly.....
Yes apologies...550 is 10 inch...here is quick compare and you will know the difference in power and cone material
Product- PROFX
If you still want to consider other subs, look at Boston Acoustics ASW650 or ASW250 or BIC America F12 or Hii100.