I personally think 18" and bigger sealed subs have made ported subs irrelevant (unless you are looking for 140dB at 20Hz). The output is more than enough for music and HT. And sealed subs don't roll off as sharply as ported subs. So you can end up with much more sub-bass on the sealed sub given room gain. At 20Hz the F18 has 103dB output. Placed inside OP's room, that number will jump up, nearing 110dB. That is more than plenty. And the distortion of the F18 is lower than the FV15HP, especially when nearing its limits.
Here are both Max SPL's compared to one another according to data-bass's measurements.
View attachment 137256
The FV15HP is most often run in 1-port mode, so that result is here:
As expected, there is a massive amount more output down low where it counts, making the vented 15" sub much more linear. You would have to buy a 2nd F18 to keep up with it. It will also be more tactile, making it a better choice for movies, hands down.
Yes, the F18 is super clean up higher in the range. It's almost unbelievable how low its distortion is above 30 Hz (but not so good below).
And a final point, I could not fit F18's in my space. I could fit FV15HP's which have a narrow 18" width.
I've owned F12s, G22s, and FV15HPs. I prefer the FV15's, even for music. It sounds just as good yet gives me the ability to bring out much more from the bottom end. In addition, I have an as yet unreleased higher-power version of the FV15HP that gives another dB or two in the upper frequency range. In sum, I think it almost makes the F18 obsolete, except for the usual reasons I recommend sealed: to reduce tactile effects or box size if you need those things.