What do I buy? Klipsch vs. Definitive Technology

Thanks everyone for their input. This helps me tremendously. By the way my AVR is a pretty old Denon 2800. Probably 8-9 years old.

I listened to the Def Tech super cubes and was not impressed. I liked the higher end Klipsch's better. I thought the sound range was way better

I own the Super Cube Reference by Definitive Tech running in line with my mains,this sub is very precise and musical if set up properly,like any piece of equipment. Me thinks your sound range that you speak of leans more towards a boom boom type of response. If so ,you will never appreciate any type of musical sub.

Go with the Boom Boom. Happy Listening...

The number one suggested position for running 2 subs is in stereo next to your mains or more accurately under your mains....  Not sure what all the talk is about placement problems with subs built into the speaker that puts them in the best place automatically. I agree with last post about your liking the boom.  Have you done any listening to these klipsch speakers you talk of buying to match this new sub?   I have never heard a klipsch speaker that wasn't xtremely fatiguing, and btw that harshness is greatly exaggerated even more in a mostly closed rectangular room if speakers are on narrow wall

That was seven years ago.  I would hope he figured it out by now.

I have extensive experience with both brands over the last couple decades. Differing technologies require fairly distinctly different setup approaches and even equipment needs, acoustics considerations, etc, and integrate differently, offer differing strengths and weaknesses, and so forth.  I do like both brands but, yes, address both somewhat differently.
With the klipschs, I can get away with less acoustic treatments, as the speakers tend to beam in mid/highs, and you can aim them for even less boundary reflection interactions.  Also, require somewhat less power, easier to driver for any receiver, and yet still sound best with warmer gear, even tubes, etc, as klipshs are ZIPPY and tipped up on top end! 
Still, bang for buck, they can play louder and punchier with solid sound propagation and intelligibility from the design.
Deftech's powered line are THE ONLY options I'd chose for their mains!  They are super effeicient with powered sub assisted designs! It makes for dynamic advantage over typical. (yes, klipsh dynamics with sub also super, compared to standard designs - also, more flexible gear selection choices. Still, must do critical setup and/or room acoustics, as sidewall reflections must be dealt with, unless longwall setup.
How big is this room?  Curious.
For average dual purpose setup, I'd probably go Deftech's more often than not, and just hide power cords, and live with it. (otherwise, build a proper façade, and do a professional theater look to front of room, and hide all your gear anyway! -sans the old school throw back equipment strewed all around the room, wife displeased look, and modernize!).
I've had good experience with powered def techs, mated to Parasound solid state in past, and even tube gear too, yes!   Stuff sound dynamic and potent enough, and still good for music, yup. With Klipsh, I DEFINITELY like tube gear in the signal path!  Mellows out, and horns are solid sounding, great for home theater, dynamic as heck for passive, and cheap!   
Good luck