I have the same Pioneer receiver and loved it for the two or three years it was my home theater centerpiece. Never did I have any heating issues, but mine was always set to 8ohms. As a matter of fact I never had any issues with the Pioneer. I have recently "upgraded" to a Marantz SR6001, which to me sounds better but doesn't have as many bells and whistles. I miss the sound retriever and dialog enhancer although I haven't really needed them with the Marantz around.
By the way, how long (or how many posts?) do you have to wait until you can post something for sale here? I want to sell that Pioneer to help offset the cost of the Marantz I just picked up. I'm also thinking of selling my backup speakers (the dreaded cousins of the Cerwin Vega D-9's) the Cerwin Vega D-7's. Those speakers have been very faithful to me no matter what garbage I threw at them (mostly metal, but that's what they were made for, right?).