I've used several of these in several cars.. You can get the same opinion from several people on DIYMA. Thread majority from people who have used them, ported, small box tuned low. They don't **** sealed, but they def have a better lowend presence ported and the response curve is very nice.You should always take opinions with a grain of salt here. Even if he has heard these subs before I doubt he's done much testing/comparison between sealed and vented enclosures. I would model it in WinISD and make the decision myself it were my project. Also if the manufacturer suggests sealed is ideal then go sealed and be done with it.
Dayton Reference 10"HO - Page 11 - Car Audio | DiyMobileAudio.com | Car Stereo Forum
Also that's the lowest fundamental tone on a bass guitar, but the instrument itself will have content lower than that, just not as it's fundamental tone. Cross a sub sharply over at 40hz and even on jazz you will hear a difference on many recordings. 5 string bass guitars in both upright and electric and go down to B0/~31Hz.
Regardless sealed is easier, if you start there you can always add a small areoport to it if you find the low end lacking.