Should i changes my sub to Fathom f112 or f113

Depending on your goal there are a few factors to consider. Powered subwoofers have become much more sophisticated with the inclusion of EQ and or room correction.

My Supernova benefitted from the Velodyne setup program. Still the Supernova is limited to crossover, and volume. IMO having multiple EQ presets with my Velodyne DD makes adjustments to film and music audio a snap. With the Supernova I have to adjust a very sensitive volume attenuator.

My experience with the fathom is simply showroom. In that context they seemed to be a fine sub sonically. You'll notice some of the review testing was done using the Velodyne program. I'm not trying to make a point for Velodyne but their day to day usability suits my requirements for adjusting the sub to fit the material I'm listening to.

Two subs can load a room better than one but it's not necessarily a requirement.

Thanks for all your feedback,so far didnt decide yet which sub should i get.

Gigolo, keep the Earthquake and get an SMS-1

http://velodyne.com/product-accessories/management-systems.html

They're selling them new for the used price. The 15 is really a hairy sub. EQ it with the SMS then run the room correction on your new 7.1.

Iplaynaked's advise is still pertinent. Spend the savings on a better pre/pro.

I'd also suggest replacing the AVR before addressing the subs. You'll almost certainly end up with some sort of digital bass management (Audyssey or similar) that will DRAMATICALLY impact the performance of the subwoofers. This may also make the Velo SMS-1 (a solid product and a very good deal, I used one for years) recommended by Vicdamone duplicative.

HT is the only area where I'd say choose the electronics first.

Marty

PS If you do replace the subs and have the space for it, a pair of 12" Rythmiks (at +/- $1600) is worth thinking about - rather than a single f113. I love the JLs, but ultimately felt that a pair of Rythmiks was probably the better deal. YMMV.