Depending on your room size the two subs could be great or way too much. I have the LFM1-EX which is similar to the X12 in size and design. I use the LFM1-EX for movies mostly but it is not THX certified. The X13 is THX certified and I would expect it to excel in the THX realm which is mostly movie tracks. If you get the X13 the extra $$$ is partly due to that THX cert and I would focus it on movies. Bear in mind that depending on the crossover used and the design of the main speakers there isn't a lot of music which goes below 60 hz so the extra oomph might be wasted on music.
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Music system
Model 990/7500/Magnepan 1.6 QRs/Technics SL1200 MK2/Aperion S-12 Subwoofer/OWA3/Sony NS75H DVD
APC H15 Power Conditioner
TV System
Large Advent Loudspeakers/ Polk center/Monoprice surrounds/Panasonic Viera 42 inch/Onkyo HT-RC260/Sony BDP S590/Directv
Home Theater System
Onkyo PR-SC886/Outlaw 7125 Klipsch RF-82 L/R,RC-62 center, RB-35 SR/SL, BENQ HT1075, Outlaw LFM1-EX/OPPO BDP-83/Directv
Harmony ONE
Blue Jeans and Monoprice interconnects
APC H15 Power Conditioner