Bottom line -- sealed boxes can sound loud too when paired with the right woofer.....
Too loud? ...no such thing!
I was using the typical 4th gen sealed box for my 12's. No complaints about bass or thump, it was amazing. As you say, way more bass than one would expect from a sealed box, but, that's our glorious rear hatch performing a bit of concert hall magic for us. You're dead on about the right woofer. My issue was just that. The entire box for the two 12's is less than half the optimal air volume for just one of my 12's in a sealed enclosure. I was mostly amazed at how well it did sound and how low it was dropping, but I always knew a woofer matched to the box would have performed better. ...and that's what people overlook, the airspace. So many buy the prefab boxes without a moments consideration as to what the woofer wants. ...but, they hook it up, it thumps a bit, booms a bit, rattles the rearview, and that's good enough. ...when they could have one speaker put into a proper custom enclosure and make the steering wheel flex front to back a half inch as their brains liquify and pour from their ears.
If I ever get another amp capable of pushing my 12's, I'm removing the seperator in the box and plugging off one of the holes. One 12 given 1/2 its optimal volume of air should sound orders of magnitude better than 2 12's operating in 1/4 of the optimal air volume.
I knew a kid back in the late 80's who had one 8" speaker in a bandpass box on a Punch 45 in the back of his 3rd gen. It was amazing, you could hear sir-mix-a-lot from a good 5 blocks away.
Sealed, Ported, Bandpass. Each has their place, pros and cons. Sealed is the best all around box IMO, never a muddy note with a sealed box, no port flutter, nice tight bass,. ...love 'em. Love band passes even more but there's not much hope of those in our cars. Recently, I lost my faithful MTX Thunder 225HO. I'm down to ONE 16 year old Bazooka EL604 in the rear on some $89 "250w" Circuit City MTX amplifier. Thanks to the hatch, it is most impressive for what it is. My car doesn't sound like it has "just a 6" in the trunk. ...doesn't sound like 2 1,200w aluminum cone 12" DVCs at a half ohm either.