I have burnt parts of my system by mismatching like that. I dont know what the specific ohms are on your HIVI but I know my 8Ohm speakers are really about 6.83Ohm. No problems, but my amp is supposed to handle 6 and 4 as well. In college I had some 2Ohm Acoustic research speakers and burnt them up in a few hours on my Kenwood receiver. I dont know why it burnt them, but the mismatch obviously ruined the weakest link in the chain.
Ever consider building your own amp? Its really pretty easy to do and can be quite inexpensive. Maybe this isnt your cup of tea, but you can pic up a surround processor and then have it control a few DIY amps to run your speakers and you will have something that (probably) will sound better than the Denon and that you built yourself. No disrespect to the Denon, I am just trying to suck you into this nasty rewarding habit we have. Its truly a lot of fun and you dont need ANY high tech equipment. Just a solder iron, solder, wire, and some components. My LM3886 sounds WAY better than my Harmon Kardon. No exaggeration at all. It blows it away. And of course they can get even better. There is lots of knowledge here and you will get lots of help if its something you would consider.
You can even buy the kits and then its just too easy
This can cost as much or almost as little as you want.