I am not clear what message you are trying to convey as the video did not contradict what I stated in my post. If it is still about the so called 8 ohm/4 ohm amp thing, please re-watch the video at around 6:50 to 6:65 where the gentleman summarized that, ....modern amp...can drive 4,6, or 8 ohm...if you have a modern amplifier......don't worry about it.
Basically, any mid level receiver, integrated amp, power amp from the major brands that people discussed on this forum such as D&M, Parasound, Emotiva, Outlaw, Yamaha etc., could have been rated for 4 ohms if the manufacturers chose to. That could mean too much work/cost, it is easier to simply rate them for 8 ohms, or they would provide a selector switch or setting to lower the rail voltage (or by other means) in order to get by certain regulatory rules, that's all.
For someone who has basic electrical knowledge (everyone knows Ohm's law right?), the issue with lower impedance is the resulting increase in current for the same power output.
For 100 W output into an 8 ohm load, the current will be equal to square root 100/8 = 3.535 A
For 50 W output into a 4 ohm load, the current will be equal to square root 50/4 = 3.535 A
So basically (as always, there could be caveats..),a 100 W rated amp could be rated 100 W into 8 ohm, and 50 W into 4 ohm. As mentioned above, some would provide a hard switch, or software setting to enforce the current limit required for the lower impedance. For many practical applications when people don't push their receivers/amps anywhere close to their limits, there should be no need to to worry about such switch/setting that if used, would limit current indiscriminately, potentially limiting the dynamics of music and movies.
All else being equal, obviously a 4 ohm rated amp should be able to handle sqrt(2) X the current, thereby can be rated close to 2X the power output, vs an 8 ohm rated amp. That's why I said what I said in the first paragraph of my post#9, instead of some sort of blanket statement.
Back to the OP's question, he didn't ask about power output, but "....upgrade in sound.." As soon as I realized he mentioned the protection light, and that his speakers are rated 4 ohms, I alerted him by asking questions regarding seating distance, spl requirements etc. That's because I suspect he needs to worry more about not having enough juice for his speakers, than the "sound quality" of his amp. I could have suggested that he get a 500 W amp and call it a day, but I typically try to avoid blanket statements. He probably does need a more powerful amp (not just a 4 ohm rated amp),but I would like him to answer my questions first.
