So you paid half price for the T15's? If so, cause in my opinion that's about what they are worth full retail no. Between the two from what I have read up on the Energy C1 seems to be the better of the two. i say that only because looks like the Energy C1 has a much better build to them, driver's are "Aluminum" type of material used. I have a pair of the Polk T15's, they are used as a surround I paid umm about 65 bucks new a few years ago. They are good, Not great, they lack inner detail I say that only because I did try them out full range just to see topend isn't that good very laid back sound midrange ok at best. Built good but nothing special about them. If someone was to use a pair of the T15's with a lil Sub so they would have better sound from TV speakers yeah would definitely be an improvement for sure. Don't know what price you could pay for those Energy C1's? but to use in a small setup for music would more than likely be the better of the two.