Somehow I missed the E-mails notifying me of a reply, missed these posts until now. Have heard great things about Sundown, while the CV was more of a shot in the dark. The Sundown according to T/S parameters would have been better in a ported box. What does the "B-stock" imply?
I ended up going with the dual 4-ohm which turned out to be the right decision as the subs seem to handle the power nicely. I was unsure what my exact tuning frequency would end up being, because the prefab manufacturers don't give NET volume, so they don't subtract port volume or driver displacement. Thus the tuning frequency will be higher than the spec they publish. After rough calculating and running some test tones through it, I can tell it is tuned roughly in the mid-high 30's range.
According to some WinISD modeling, the CV would have a huge output peak around 35-45 hz, and it sure does. Required a fair bit of tweaking the EQ on my head unit to get things evened out. It's ridiculously loud and sounds great with rap, R&B type stuff with lots of sustained low notes, even quick transitioning ones. It isn't as good with rock, or more dynamic music with more punchy and/or higher notes.
I'm questioning if I should have gone with sealed boxes for these, but I haven't played with it enough yet to determine if ported was a bad idea. One thing is for sure, is they are a great value for the price, more than enough output and the sub doesn't have to work too hard-- handles power great until you get below 30hz then you have to tame the movement with the subsonic filter to keep the sub from bottoming out.