New/Used Amp recommendations for about $3k-$4k?

no idea what improvement is possible over the emotiva’s you mentioned, as i have never heard them

in the price range (roughly) you mention, used, i would personally lean towards a hegel h20, or if less watts is needed, a pass or first watt amp

these are exceptionally good yet affordable solid state power amps

the benchmark amplifier is well known for its very clean detailed (if slightly lean) sound

I don’t think the monster preamp as mention above is a bottleneck because I’ve heard these speakers on the same preamp with the XPR-1 mono blocks and they sounded so sweet and detailed. 
I’m looking for an amp with as much detail as the XPR-1’s but don’t have the big form factor. I had to keep the XPR’s out on the floor on granite because they were monster sized amps and weight over 100lbs. 

My 8805 has a very nice 2 channel setup feature that allows for some nice 2 channel stereo listening. It’s not just a movie preamp. 
I have the same four sub woofers in each corner of my room for lost of bass. 

Alright people,  

I ended up getting the Parasound Halo A21+ in black. 

"I could-a had-a VK"...

Nice amp.  Congrats.  You still need to try a good 2-channel preamp — it’ll be a big improvement over your Marantz that may sound “nice,” but a lot of things sound ok until you hear something better and then it’s not so “nice” anymore.  I just think your speakers and new amp outclass your processor, but do as you will.