Well the sherwood has a couple of known problems. The stand bye mode has quit working completely. And the two subwoofer modes normal and sub plus only the syub plus works. On normal the sub doesnt work at all. Is it the cause of everything? I dont know. Is something wrong with the Sherwood? Yes. Avs I am looking at Denon AVR 3808 and 4310 and the Onkyo Tx-NR906
1. What do you mean when you say the standby mode isn't working?
Is the power button on the front panel of the receiver in the detent position? Does the power light switch between blue and amber when you use the remote?
2. As far as the subwoofer modes not working, that seemed to only occur when sourcing from the OPPO. You have been given suggestions that your set-up in the OPPO may be wrong and you have not responded to any of them. I just looked at the OPPO manual on line and the audio set-up section is very complex and can easlily be done wrong.
3. The Denon receivers that you are looking at are more complex than the Sherwood that you already have; so you may just be digging a deeper hole if you don't find out what is wrong first. You would get lot's of help if you would respond to suggestions already offered.
Bill