I will echo what others have stated. Your current receiver should be ample for your listening area. By the way, from what I have come to understand, Denons are fairly true to their advertised power ratings.
Lastly, keep in mind that there is a dimnished scale of returns regarding power and SPL. In other words, if your current system is 100w/channel and you get 110db on a sound meter when your receiver volume is set at 'X', by switching to a 200w/channel receiver (increasing the watts by 100%)you will not get a 100% increase in SPL at volume 'X'. Actually, you would only be at 113db...a net gain of 3 decibals.
Here is a good article to read on the subject:
http://www.audioholics.com/FAQs/wattsvsdBs.php
