Your question has already been implicitly answered. None of those PSB subs are suitable to go with your Dali Mentor 5s. They are not of sufficient sound quality to match up with them. Indeed, I would bet that the Dali Mentors produce much more articulate bass down to their low frequency roll off than the PSB subs, which would negate your reason for buying those particular subs because you wouldn't need the high pass filters. I have a 10" ported sub in that class (price/performance range), and I found that even the B&W 601 bookshelves that I used to have produced more detailed midbass (and they are bass shy) over the 10" sub (I now use that sub in a computer desktop 2.1 system). No one here is every going to recommend one of those subs to use with your setup. It would be a crime (lol).
Your problem is electronics, not the subs. If you get the Emotiva USP-1
, you would have a pre-amp that would allow you to run any good sub. It has built in high pass filters. You could either run it as your main preamp with all of your components plugged into it, and then just use NAD as a power amp (plug it into the main amp inputs), or insert it into the processing audio chain on the NAD between pre out 1 and the main amp inputs.
If you have that, then the Rythmik F15HP
would be an excellent choice. You need a high output sub given your room size, and the Rythmik subs are acknowledged to be some of the best sound quality in their price range, way better than what you would get out of the PSBs.
If you don't want to deal with an extra piece of electronics, it looks like the SVS PB13-Ultra
has low and high pass filters like the PSB subs (verify this by calling SVS). But once again, the SVS is in a class that matches better with your Dali Mentors.