My first post as a new member. I've read everything I can find online about these 2 models (even the AK Pioneer components specs database). I have a SX-9900S but it has too many small useless buttons and the tuner preset buttons are way too small, the front panel is WAY too condensed and complicated. I found a VSX-4900S on CL for $20 and made plans with the seller to pick it up at 5pm. He just called and said sombody showed up at his door unexpectedly and he just had to sell it to him. I found out a lot about the VSX-4900S and its buttons are bigger and easier for my wife to figure out. I've only been able to find out that the 4800 is also 100 WPC (front only, same as 4900S) and its remote looks nicer than the 4900S, and it looks just like the 4900S as far as I can tell from the fuzzy pictures I've found. I've found a VSX-4800 for sale but can't see any difference except the remote looks better. The same user manual is for the VSX-4950S, VSX-4900S, and VSX-4800. Anybody know what the S stands for? They all seem to have surround mode. I had to buy the user manual for my VSX-9900S. I can't find any free source of Pioneer receiver manuals. Does anybody know what the difference is?