First of all, stop calling them folded horns. ALL the horn subs are folded - the front loaded horns, the rear loaded horns and the tapped horns are all folded. These are front loaded horns.
Front loaded horns are fine for house and dubstep. THESE particular front loaded horns that you have chose are not good for much of anything.
Like I told you a month ago, you need to state your goals clearly if you want any recommendations.
http://www.diyaudio.com/forums/subw...oop-folded-horn-subwoofers-3.html#post3410738
As far as I know you haven't attempted to answer a single question I asked yet.
The 3 main questions are -
1. budget (do you already have the drivers and how much money do you have?)
2. required spl (required spl at the furthest distance of interest)
3. required frequency response
#3 is the one in question with these horns you've chosen. You can analyse your music with software to see how low it goes and determine from there how low you want your subs to go. The lower you go the larger and more expensive the system is going to be.
For an idea of what this will sound like, if you have a system that's relatively flat and a multi band eq, you can use the eq to bring 60 hz down by 3 db and everything below 60 hz pull it down all the way. The eq will probably only let you pull the lower bass down 12 db (which isn't nearly enough to reflect how bad these subs will be) so listen to that and imagine even LESS low bass and decide if that's what you want.
These speakerplans horns will pound you silly above 60 hz but they won't do anything below 50 hz at all. If it were me, I'd shoot for extension down to AT LEAST 35 hz for modern music. There are lots of horn subs that can do that, which one to pick depends on how loud it needs to be.