I would wait and see how the Denon performs.
Most "FAMILIES" won't be listening to 100dB volume, but rather more like 80-90dB. The Polk rti a7 has a sensitivity of 89dB/watt/meter.
If you are sitting 4 meters away from the speakers and your volume is 90dB per speaker, then your amp only needs about 20 watts of power per speaker.
If your volume is 93dB per speaker, then 40W.
If volume is 96dB per speaker, then 80W.
If vol is 99dB, then 160W.
Doubling the power (from 100W to 200W) will get you 3dB of extra volume.
So I would wait and get a 200W amp IF the Denon TRULY needs the extra power.
http://www.crownaudio.com/en/tools/calculators#amp_power_required