Hey @smicale, welcome to the community.

The change in EQ you’re experiencing is likely due to the differences in connecting the AVR to the Connect’s outputs. When you use the RCA out jacks on the Connect you’re using the Sonos DAC, however when you use the optical out you’re bypassing the Sonos DAC and all of that signal processing will be handled by the AVR. You would need to make any EQ changes on the AVR itself since the Sonos Connect is no longer colouring the sound that way.

In regard to your planned setup - yes, that configuration would still work. Volume control would be a bit more difficult in that setup though, as you’d need to balance the volume of the Connect in the Sonos app for the attached sub, and use the AVR’s volume controls for the TekTon speakers. Personally, I would keep the subwoofer hooked up to the AVR and set the Connect to a fixed volume level so that volume control is just handled by the AVR.

I hope that helps! Let me know if you have any other questions 

Thanks James! I really appreciate you chiming in here. So If you think it is best to connect my SUB to the Subwoofer out on my Yamaha AVR should I connect the Sonos Connect to the AVR via RCA or Fiber  connections?

No problem! That choice comes down to personal preference. I would test it out for a day or so on each configuration and see which one you like best. It might take a bit of time to dial in the right EQ on the AVR when using the optical connection, but it’s all up to personal taste 

Another probably dumb question. Will the AVR control the sound output for the subs volume or will the volume control on the back of the sub do that?

The volume control on the subwoofer itself will handle the basic volume, but the AVR may have some sub specific settings such as crossover or options to boost the bass output. Take a look through the AVR’s manual or settings to see what options you have 

Thanks again James! I did go through the Yamaha HTR-5490, this AVR is probably a good 15 yrs old but I think has enough power to use it just for a 2 Channel setup of the TekTon’s and the Sub. I am not seeing any settings in it to really adjust the subwoofer. If I understand things there is no need to use LFE with this type of setup as that is really more for Home Theater setups. Once I get the TekTon’s hooked up I will have to do some playing around like you say and see what gives me the best option. I am also looking at a Emotiva XPA-2 Gen3 2 Channel Audiophile Power Amplifier to replace the Yamaha if I can’t get the sound I am really wanting. We’ll see how it goes!