FWIW, I have owned two Onkyo receivers. The first "real" receiver I owned was the Onkyo HT-R160 which was very similar to the 607 I believe. I think I got this back in 2010?? I then upgraded to an 809 sometime last summer. Obviously I haven't owned either of these receivers for very long, but both still work well.
I gave the HT-R160 to my mom for her cottage where it is
very humid all the time, with no AC. She only runs two speakers off it, one inside the cottage, and one outside the cottage. No need for "good" sound there, just something playing in the background for me while I split wood outside and she paints inside. Either way, it does still get hot... very hot... time to time and it's sitting on the top of a curio cabinet thing with nothing above it whatsoever. Although it does take several hours to get to that hot, and being 95-100 degrees everyday with no AC doesn't help the situation I'm sure.
The 809 still runs everything I have to throw at it. I don't have an external amp of any kind, but I also don't listen at very loud levels whatsoever. It's more/less background music running at 60-70 dB with peaks, if you want to call them peaks, up around 75-80 dB tops.
Both receivers have never been driven hard, but both are still cranking out juice just fine. I have had to call Onkyo's customer support once for the 809. During a firmware update, I lost power for a few minutes. After power came back on, the receiver would turn on, but not play any sound through any speakers. I called customer support and the only "help" I managed to get was someone telling me to make sure the power cable is plugged into the wall correctly, knowing that it turns on but isn't powering/recognizing any speakers no matter what I tried. They gave me an address to ship the receiver to to have it fixed, me paying shipping both ways of course which isn't cheap being that my college is in the middle of BFE. I played with it some more myself, and managed to pull up the firmware update and let that go through all the way and everything seemed to work after that.
Either way, I got that Denon as a backup should anything ever happen to my baby, I mean Onkyo.