You wanna reword that a bit?
You connect outputs to inputs. Now, try it again but have some idea of what impedances you're talking about here.
By the way that "sweet sound that only a tube amp can provide" boils down to a heaping helping of even order harmonic distortion, particularly when driven into clipping. Is that what you really want?
In any case, you would have to connect the tube preamp outputs to the Marantz's main power amp inputs, assuming your receiver offers that option. I know you aren't considerig connecting it to a line-level (aux) input on the Marantz. That would be foolish.