I'm not so sure there is a definitive answer to your question. My sub is a sealed design with an 8" driver (13' x 18' room) and I have great integration. I've also used ported and I have to say sealed is better for music in my experience.
Go dual small sub, switch to closed sub or buy a bigger sub?
I bought my first sub 2 months ago: an SVS PB-1000 and I loved it .. at first. Maybe I have a case of upgrade-itis but I want more/better/different without being able to pinpoint what I want.
I have the PB-1000 running in my livingroom (128 cubic meter or around 4500 cubic feet) and I ran the Audyssey EQ. It seems there is a lot of headroom (gain is at 50% and audyssey still set the subwoofer trim to -5db) .. but since so many people seem to prefer bigger subs I fear I am missing out on something. Should I consider buying another PB-1000 and perhaps experience the magic of dual subs people proclaim or should I just go closed sub rather than ported sub since I prefer music over tv/movies, and then simply get a bigger one e.g. SB-4000?
Note: I am not in the US, so no SVS trade-in upgrade option unfortunately.