A few years ago I picked up a pair of the original Klipsch Heresy for my son. I used them with a recapped Carver MXR150 receiver. I found them to be very accurate and nice sounding at low volumes only. The horns, for me, were too harsh with volume. The low end wasn't overly low and the top end wasn't very high. Frequency response: 50Hz to 17kHz.
I have several pair of Heresies, although none are III's. As with any of the Heresies I suggest using a sub to enhance what they won't produce on their own. If you can pair the Heresy III's with a pair of subs I am sure they would sound amazing. That is how I have mine set up....and they sound fantastic.
I've had the series one, two, and three. The twos were my favorites, but don't expect low bass from them. The good news is that since they roll off at about 50 Hz, you can use just about ANY sub - run the Heresys full range & use the low-pass filter on the sub for a good match. It's easier than it sounds.