The F8 is a great subwoofer, no doubt about it, but I would have to give the nod to the E112. JL Audio doesn't make budget products, but when you hear one you realize they don't cut corners either. Not that Rythmik does, but sometimes spending more gets you more.
Just my 2 cents. If you factor in price it should be two F8's vs one JL Audio E112s.
Or better yet two Rythmik F12G.
I have heard the E110 in a showroom setup really incorrectly and I could still tell it was an awesome sub. After playing with the settings it was out of this world. I just could not pay that much for a single sub.
Also I *wanted* 16hz performance for music and both the E110 and E112 fall short. Sadly my Paradigm Servo 15 falls short also.
Dual F12/F12G should do the trick. I wish Rythmik would do a 15" paper cone but I'm guessing demand would be low.