Let's not forget that amplifier impedance ratings are done at full output power. If the manufacturer wants a lower impedance rating he just needs to lower the power output rating. I don't know about you but I never get close to full output power on my receiver. I think the highest level I've ever hit is 18 watts. The speakers are 6 ohms and 88db sensitive. My subwoofer amp carries most of the load and 18 watts drives my 88db rated speakers to uncomfortably loud levels. I've never measured my bedroom system but here are some facts. The room is 12X22 feet opening up to 16 feet at one end. Big bedroom. My speakers are 4 ohm nominal and 87db sensitive there. I do have a powered sub. The receiver is a bottom-of-the-line Pioneer (VSX522 under $200.) rated at something like 80 watts per channel. I can play the system loud enough that my wife complains from downstairs without the receiver getting more than comfortably warm. It isn't even well ventilated.
I agree with Arny. Something is wrong with Sales 5's situation. It doesn't make sense. Either he plays at abusive levels or something is wrong with the equipment. I read reports of thermal shutdown but, in my experience, that is usually due to lack of ventilation rather than speaker impedance. I've never encountered it personally nor do I know anyone who has.
If you play at normal average levels - 75-85 db - in a normal listening room in a normal home, any receiver should be able to play a vast majority of the speakers available in the industry at any price. There are a lot of people around trying to sell you amplifiers and instilling fear of low impedances is their major tool.