No real cons, great low bass performance and transitions very well to the midbass drivers. I guess if anyone had a complaint, the surround tends to dimple (by design) at high excursion since it is narrow, this gives a little mechanical noise if you're close to the sub, but I don't really push it that hard so it isn't a problem for me. Biggest ID Max is a 12", it has a surface area deficit against an Avalanche 15" from the get-go, that's between 2-3db right there. Avalanche would be noticeably louder.
Crap, I forgot to ask you what kind of box your idmax is in...thanks. Mine would probably go sealed just because its my first time building a box. Thanks again.