I know how the size affects the low end. As far as not being able to reproduce frequencies below 80Hz or 100Hz, that's wrong. If it's in the right box, it'll do fine. A small diameter cone can have a very low F3, especially if its mass is a bit higher and the motor assembly is exceptionally strong, so it can respond better to the cone's momentum. I'm not sure it can even be called a 'subwoofer' if it doesn't go below 80Hz (not that manufacturer claims are all truthful, but I haven't seen Jamo cheese on their specs).
My main speakers use Peerless 6-1/2" drivers and in the box I'm using, even if I block the port, they go below 80 and with the port open, there's a little bump at about 50Hz. I have them about 1' from the back wall and about 22" above the floor, toed in a bit. The size of the room will matter when it comes to the rolloff, but they can definitely go below 80Hz. I have used TrueRTA and Room EQ Wizard and they show good energy below 50Hz.
Jamo is now owned by Klipsch and as far as I'm concerned, it's not necessarily a good thing, but that's because I worked for the second dealer Jamo had in the US and I remember when we started selling their speakers- immediate acceptance and almost no problems (other than the occasional case of abuse). I still have a pair of J-101 and they have all Phillips drivers. Klipsch bought Jamo because at the time, Jamo's founders wanted to retire, so all of the stock was put in a holding company, to make the sale cleaner. Also, when Jamo was sold, they were #3 worldwide in the number of speakers sold, behind Bose and the Harmon
Group. Not JBL, Infinity or another of Harmon's brands, but the whole group. That's pretty amazing for a company that didn't have particularly good brand name recognition in the US. Klipsch wanted market share and didn't need to improve the line, although a few models needed to go because they really weren't what I would consider to be true to the Jamo tradition, even as relatively short as it was before the sale. What I have heard from people who were there at the end, Klipsch is basically leaving the design to the main office in Denmark, which I think is good. They lost just about everyone at the Chicago office because nobody wanted to go to Indianapolis. I suspect that some just couldn't do it, possibly because most of them came here from Denmark and had worked for Jamo before they came to the US but also because their life was in Chicago and they didn't want to leave friends and family. It's not that far away but....
I have a Jamo A Sub.3, which is a ported 10". My living room isn't that huge and I don't want to be overpowered- I did car audio for over 25 years and for a long time after I got out of that, I didn't want to hear much bass because everyone wanted to be heard for miles around, and I hate that sound. My sub does fine below 30Hz, according to the measurements and while vented isn't my favorite sound, it does well for music and movies. Sound effects can definitely be startling and music sounds very real. It's not as good as my EV woofers (I had a pair of 30W), but it's decent enough.
I'll agree that the sound from a 12" has more balls, but for $99, this one should work well. If it's close to a wall and/or corner, it'll have more impact, as we know. Funny thing about so many of the reasonably priced drivers that have good reputations- they're made in the same factories in China. Even many of the well-known European brands have them made there but they design them in their home country.
I would like to hear more of the Dayton line. Maybe Parts Express will do a road show or go to CEDIA or CES (I haven't been there since they stopped having it in Chicago).
My opinion is different, but so am I. After more than 30 years in the business, Oh, yeah- I have some opinions, all right.