Budget Basement System Troubles!

I've encountered 2 more problems with my basement system and they're driving me crazy.

Switched from a Logitech BT receiver for my late model Marantz AV receiver to a WiFi receiver from OSD, called Nero Link. I thought WiFi streaming would sound better than the BT, not only does it not, but for some reason the center channel will not play when using it. The sound is awful, very tinny, so bad it is literally worse than the sound from my iPhone. Could it be because the Nero Link uses a 3.5mm to RCA to connect, and the BT uses regular RCA interconnects? 

I bought a Sony SACD player and I hooked it up using the 5.1 RCA interconnects, and when it plays it is SOO loud. I have to turn volume all the way down. I know there are adjustments for speaker levels and the like, but I can't seem to get to the correct menu to adjust them, if this is even the problem. The manual says to turn the jog dial till you see "LEVEL ADJ" but it never shows up. What do you think the problem(s) is/are concerning this?

I'm at a loss here, I would greatly appreciate any advice you can offer.

Thank you so much!

You're already gone through three receivers. That ought to be enough to know receivers aren't all that. I'm trying to be polite.All your troubles, all of them, stem from overly complicated receivers trying to do too much. One more switch, this time to as simple and quality a plain old stereo integrated amp as you can find, and you will begin to see the light.
YUP, pick your poison, and go from there. Most of the Sonys I use use(ES series) have a remote and I adjust from there. You have the Sony remote that comes with the unit (s)?

No bad or loose RCAs. You've checked the easy stuff, right?

As far as the type of surround, Dolby, Atmos, Mac, ect The disk has to match the players. Like losing a center channel, low volume.  I don't use surround, just stereo. In stereo mode it sound it sounds funky to?

How about just the Sony as source and into the receiver as a stereo unit. no 5,1 stuff?  That first ay. Good cables, stereo only..

Happy hunting..

Why are you messing around with weird stuff like Bluetooth receivers and WiFi receivers?  What didn’t you like about the Marantz AVR?  I have two Anthem receivers in my house with ARC and I love them.  I don’t care for the Marantz house sound but I would definitely go with one of them over the weird choices that you’ve made.  You’re trying to run a SACD player through one of these gizmos?  Good grief how does that work?  No wonder why it sounds bad.
  At the very least, I would stick with a conventional AVR, especially if you are trying to run traditional components through it.  Tell us what was wrong with the Marantz and then perhaps we can help you more.  Sorry to sound like a jerk, but you have made some choices that are head scratchers...
Sorry, I must have stated something wrong. The BT and WiFi receivers I'm talking about are the "add on" type that allow you to stream through one of those formats using your older, existing non BT or WiFi receiver. Yes, they are gizmo-like. And no you certainly can't run a SACD player through one. They simply receive the signal from your phone or tablet etc, and you hook it up to one of your open inputs and it plays the music. They are little boxes, smaller than a pack of cigarettes usually with one button on it to make it visible to pair with your device. I use the Marantz AVR for everything. Check Amazon for OSD Nero Link and you will see what type of device I have been using. And there is nothing wrong with the Marantz. Very pleased with it.  I recently learned that HK makes one and I think I'll give it a whirl and see what happens. Thanks!