New high end processor

Still pondering.... I do want the all in one box solution at least for this time and not crazy complicated to set up. And yes I do like music which has been missing in my room. 

So, if you get a prepro you’ll need another box to power your HT speakers, so two boxes right? The Anthem MRX 720 AVR is on sale at Anthem for $2k, and I’m not sure what else the AVM 60 offers but the 720 seems pretty dang good and takes care of your HT processing/amplification in one box. And it leaves you $3k for a nice stereo pre, which you just take the front L/R pre outs from the 720 into the stereo pre and you’re done again with only two boxes, but now you’ve got a superior preamp in the chain for critical 2-channel listening. Switch between HT and stereo with the push of one button, and in 2-channel the Anthem is completely out of the chain. Couldn’t be simpler really (I did this for years before I had a dedicated listening room), and that’s certainly what I’d do if I had your speakers and amps. FWIW, and again best of luck.

On paper, the AVM60 offers two advantages that may or may not matter to you: balanced outputs and a dedicated headphone amp. In reality the main advantage is the ability and flexibility to add better and or more powerful amplifier channels than those built into their receivers. 

The OP has mentioned that he has amplifiers sitting unused, waiting to be installed with a new prepro.  I'm not clear on whether those are new amps or old ones that he's had for years.  It sounds like there are several options being considered, 5.1 vs .7.1, atmos, avr vs separates.

If the amps are going to be employed, it goes without saying that there will need to be rack space and proper heat management for them.  As long as those needs can be met, I'd encourage a prepro, and you shouldn't need to spend anywhere near 5k.  Any model selected would be a MAJOR improvement over the currently being used Denon 3400.

The Marantz 7705 would provide everything needed and be thousands less.  They have the Audyssey room correction system, which is widely used and almost the industry standard.  Integra has Audyssey as well, where as the Yamaha model mentioned has their own room correction.  

All of these units have features, bells and whistles and connection options that may overwhelm.  No getting around that.  

Gonna pull the trigger on a 8805 from accessories4less. Question, as this is my 1st Pre pro and amp hookup, do I use balanced or un balanced cables?

Thanks