Help! Receiver or preamp? Im overwhelmed...

What’s your budget?

I have a Rotel prepro, and if you like the sound you’re getting now I wouldn’t recommend Marantz, which has a very different sound profile with a softer and less detailed treble but a fuller, richer midrange.  If you’d like to keep the basic sonic traits you have but just improve it across the board I’d go with Anthem.  There’s a used MRX720 on US AudioMart for $1600 (I’d offer $1300 as Anthem just introduced their new models) that would provide better 2-channel performance but also much better multichannel processing and room correction.  It’s a bit over your budget but a nice step up if you can swing it, but if not you can probably get a used MRX520 for around $1000 but I think is a step down in their ARC room correction.  Personally, if I’m you I’d buy the MRX720 as it’ll give you great all-around improvements and I think you’ll be thrilled.  Anyway, FWIW and best of luck. 

@oringray — Go away Skippy.  Nobody wants you or your game here — this is not the place.  Shoo!!!