New to this hobby please help me

i will add that i want great separation of musical instruments in my listening i like it when every instrument is so defined that i cant figure out which one to listen to !!

What you’re talking about is imaging and 3D soundstage, and there are some speakers that do this better than others.  I’ll point to ProAc, Joseph Audio, Vandersteen, Usher, and Fritz just to name some in case you can find dealers for any of them they’d be well worth searching out.  One idea is the Joseph Audio Prism that’s $3700 new but there’s a used pair available for about $2k from a reputable dealer who allows for returns, and you’d be hard pressed to find a speaker with comparable imaging/soundstage near this price.  It offers a lot of their highly-regarded $10k Pulsars at a fraction of the price.  Just one idea FWIW.

https://tmraudio.com/fresh-arrivals/joseph-audio-prism-bookshelf-speakers-burgundy-pair-s6ig/

Incidentally, if you’re serious about 2-channel you’ll wanna add a good stereo integrated amp you can easily integrate with your Marantz that will up your performance considerably.  The Marantz is a huge bottleneck to good stereo performance, and although something like the Prisms can sound good with your AVR you won’t be getting all they’re capable of (or any good speaker for that matter) until you can upgrade your stereo preamp/amplifier situation — something to look forward to though!  Hope this helps, and best of luck. 

https://speakerchoices.com/

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. . . i will add that i want great separation of musical instruments

Easier said than done. 

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Check out Virtual Systems here.

I have Goldenear Triton One Rs and am very happy with them. I went to the Orange County audio show this summer and have listened to music at multiple stereo shops and audiophile friends homes. I would buy the Triton One.Rs again. I think the t66s are just a little smaller but still with a powered base.  $3,800 for a new pair is a great deal.I have no affiliation with Stereo unlimited, the San Diego dealer I assume you are talking about,  but can say I like dealing  with them.

The SVS Ultra Evolution family of speakers is about the best bang for the buck you can find.  There are three models at different price points, below, at and above your budget.  Crutchfield sells them with a long trial / return / money back period.

Personally don’t care for Golden Ear speakers, much too bright and fatiguing for my taste. 
 

Of the dozens of speakers I have owned and auditioned, the following are by far the best value and most versatile. Essentially $15K+ performance for $4600:

https://philharmonicaudio.com/products/ht-tower

You can get similar sound quality from DIY kits, but you have to spend nearly as much, and still assemble and finish the speakers yourself.