The number of watts isn't as big a deal as you're making it out to be. Not familiar with the particulars, but Klipsch generally are very efficient speakers and likely you're just used to the spl you got before using the same avr. As a quick rule of thumb, takes a doubling of power to raise your spl by 3db. A few watts doesn't put a big ding into that, especially only 5 or 10, and really not even 35. Not all watt ratings are equal, either, in any case.
If you want some serious power you'll need to add outboard amps (if your avr has pre-outs).
ps Grabbed this for the amp spec on the 1613 The Denon AVR-1613 is equipped with a 5 channel power amplifier rated at 75-watts (into 8-ohms, at 20-20kHz, with 0.08% THD, driving 2 channels