everything sounded great until the upgrade

You went from a vintage receiver to a modern integrated that’s quite the sea change. I’d say give it some time maybe a week or two of constant play then throw the Marantz back in the system and see how it compares. You may find it sounds muddy and slow then again you may not. Good luck!

There has been an evolution, among the majority of brands, toward more and more “detailed” sound that means a leaner sound with less upper bass (that bass obscures higher frequency detail).  It seems to be what most buyers want.  If you are in the minority, you have to either look for vintage gear or the brands serving outliers.  I happen to like a warmer sound, which is why I favor low-powered tube gear from certain brands, such as Audio Note and Synthesis, and solid state from the likes of First Watt.

pretty profound advices, thank you all.

I just spent 2 hours playing LPs and I am a lot more appreciative of the sound now. I gotta do something about the CD player. - even the connection is weird, I have to wiggle the cable sometimes to avoid static 

You didnot say what amp, and more importantly how many hours on it.

for breakin 

I own an old Marantz like that. It was my Dads but I am not sure the model at the moment. Anyway old Marantz is super warm and I used it on some bright B&Ws with good results. 
 

I am a musical fidelity fan and have heard them sound great on a pair of wilson Sophia 3… tons of bass slam. But in your situation I personally would sell it. While good no point in buying colored speakes to work around a sound you don’t like. 
 

Anyway nothing new is as warm as old Marantz really. I think some McIntosh amps are similar to Marantz’s house sound ( I own both McIntosh and Marantz). Maybe something like the MA352 would do the trick as it is a touch warm or older Mac amps. The newer ones from the current line are more neutral.