No doubt, you have to listen to your system with and without and decide which sounds better...and in my own system, no doubt at all, much better with the preamp than Oppo direct to the power amp..in the mean time, just for fun, check out this video...
https://www.youtube.com/watch?v=Dh27E7YKN9s
https://www.youtube.com/watch?v=Dh27E7YKN9s