10's with more port area or 12's with less port area

[Neo_frog]

You will not find $100 subs that sound better than 9510s.

And to your original question, I just don't understand why everybody is so hell bent on meeting space and port "requirements". They are just a reference. You can manipulate both the response and power handling by going smaller volume with bigger subs.

If you make the port a smooth transition from box to cab, low port area turbulence will drop significantly. You will have more cone control and have some scalability for power. Especially since you want "both" SPL and SQ. An efficient, smaller box with more power will add to both if it's done right.