Generally speaking, vintage sounds better. In this case we’re talking about a 50 wpc modern amp vs 35 wpc vintage. Neither one is going to win any awards or keep you from looking for a better amp. Now bump that sx up to something that starts with a 9 or a 1 and it’s going to take well over $1,000 to buy something new that’s better. When it comes to the mass produced products like this, they were better made 40 years ago. They just used better parts and more material. I bet that sx weighs about 15 to 20 lbs more than the onkyo. Some of that is the face plate, cabinet and tuner but a lot of it is the power supply and transformers. Before 1980 they measured watts differently. Today they give you the peak number. That onkyo can get up to 50 at its peak but that’s not the average. The sx is giving you the averag at 35wpc. I’m guessing they would both clip at the same volume running the same speakers. That is really the big problem with lower powered SS amps, they will clip if you push the volume and you can blow a speaker. Also, just because something is old doesn’t make it good. Once you get beyond pioneer, Sansui, Marantz or McIntosh, those amps from the 70’s get very suspicious. Old or new, there’s no such thing as a free ride. The good stuff is expensive.