I do use the video inputs on the back of the receiver. Onkyo is known as a great manufacturer of audio components. The chance the issue is my receiver is slim to none.
Wait, hold up here... I'm having a hard time finding specs on that table but does it include a built in RIAA phono pre? If not, then you're never going to get proper sound out of it unless you are hooking it to the "phono" inputs on your receiver.
That said, that does not explain sibilance or surface noise. Sibilance could easily be cartridge setup; surface noise may mean you need to step up your vinyl cleaning game.