To me, Klipsch and Def Tech sound very different. FWIW, I prefer Def Tech, which I feel has a more laid back, "warm" sound. To me, Klipsch speakers were "brighter", with more emphasis on the high end of the spectrum. My dealer was really pushing Klipsch on me (even though he sells both brands). With that being said, don't let the dealer talk you into anything. Let your ears tell you which you prefer. They're both reputable manufacturers that stand behind their products.
Some people like Klipsch because they make very efficient speakers that are very easy for any amp/receiver to drive. I personally find them fatiguing to listen to for more than 10-15 minutes.
Conversely, some people absolutely HATE Def Tech, especially their bipolar speakers. Granted, the bipolars are more difficult to set up correctly than the direct-radiating Klipsch. Also, many people think that Def Tech "buys" their favorable reviews with the amount of advertising they do. Whatever. I think they're one of the best for home theater use, since they provide a very large soundstage, but are even good (not the best, but good) for 2-channel audio , again, if positioned correctly.
Try a different dealer. Don't be afraid to shop around. I know it's easy to get antsy when you're speaker shopping, and you probably just want to get it over with. But whichever brand you go with, it's going to be a fairly large investment, and arguably the most important for your long-term enjoyment of your audio system. Most importantly, have fun with it, take some of your own CDs when you're shopping, especially your favorite music that you know extremely well. Then whichever speaker reproduces the sound the best to you, go with it.
Two things are infinite: the universe and human stupidity. And I'm not sure about the universe. -- Albert Einstein