Get the Oppo. It's the shortest possible chain.
Jeff Bagby, at a recent event he held, reinforced a point that I always like to make. Now this is in the context of passive cross-overs but it holds true for the bigger picture also:
Jeff held a day long PCD class. At one point he's holding up a capacitor that is in the $200 range. He goes on to point out that this $200 capacitor is merely an attempt at doing the LEAST amount of damage to the signal.
My system follows suit: A modest computer (under $400). A $185 high quality, respected, well engineered Sound Card by an outfit with decades of experience making silicon for audio work, and a well engineered by an outfit with decades upon decades of experience making amplification work.
Then out to the speakers which is where I spent easily 90% of my investment. I have ~ half the $$ of what you are going to end up spending in my setup and guarantee your setup, no matter the pre-pro and amp you end up with, it can't run with what I'm running. It's about the speakers. Period.
I believe you are tying yourself in knots here. I will say it again: You need to find an A'her that is willing to help you in situ by getting one boutique pre and either the Marantz, Denon, Oppo. Put everything in pure direct mode and throw a towel. You need to find some unsighted truth to help you see your way through this.
I need to ask: Are you happy with your current speakers? You sold ALL your Emotiva in what seemed like 24 hours. Sell the Sierras. Get a $3500 budget. Spend $2700 on speakers and $700 on an integrated amp and change the entire calculus of your listening experience.
I'm trying to make this post as honest as possible. After realizing the multiple threads you have initiated, all the component swapping etc, I just circle back to maybe it's your speakers.
There isn't a day that I don't listen to my Statements that they don't put a huge smile on my face. All with a sound card that cost $185, and an amp that cost me $369.