I've been there, done that.
Used to have a receiver, some Marantz unit, then later upgraded to the now-discontinued Sony TAE9000ESD(pre/pro), which was not far short of some of the higher end pre/pros costing 5x.
I moved out of that giant-killer Sony unit to the Yamaha, and can safely say that the Yamaha better the older Sony in every area- bar none. Details, transparency, soundstage, sound & image panning cross screen, front to back, what I would call cinematic scope, is just done so much better. Plus the dirt-cheap Yamaha comes powered(!)
The only separate pre/pro that I would consider an upgrade from there would be one of the Meridians (8x $$$$).
Even using the Yamaha in stereo mode, I find its transparency amazingly good. Used in hi-res digital playback(DVDA & SACD), I don't find myself lacking in dynamics, soundstaging or blackness of background.