Which surround sound processor $1k used

Time to replace my Emotiva UMC-1, which is breaking down (don't want to send it in to fix it yet again, it's been a lemon the whole time). Anthem AVM-50? Marantz 7703? Something else? I don't have a 4k tv yet and there's not much content in dts:x but that stuff is coming and I don't want to keep upgrading, so I'd like a unit that is up to date with sound and video formats. Similarly, I don't have speakers in the ceiling or the side walls but could in the future. Two-channel stereo is a separate system so this is just sound and video quality for movies, etc. I'd like it to sound as least as good as the Emotiva, which was a steal but never worked consistently. Theta Dreadnaught-2 amp, Snell XA speakers, Rel sub. Thanks. -Dave
The Anthem AVM 50 does not support Dolby Atmos or DTS:X, but you can still play those discs through systems for backwards compatibility.  The newer AVM-60 supports them, but the 60 typically goes for $2k used.

Marantz AV770x are very nice processors.  They have excellent power supplies and discrete analog output stages.  Marantz will likely sound more natural and more engaging than other processors, but they are voiced warm with rolled off highs.  That being said, I have been impressed with this processor.  I think the 7703 is likely going to be your best bet.  It's going to be hard to find a good processor with your requirements at the $1k level.
Thanks for your response Auxinput. Seems like Marantz would be great for music but I'm wondering if "warm with rolled off highs" is right for movies. Should I go with a new model from something more mainstream like Yamaha or Denon? Anyone have any other ideas?
I had the Marantz AV8804 in my system for an afternoon.  A friend brought it over to demo/test.  I was actually very impressed with it for audio.  It does have good impact.  However, when I switched back to my Krell S1200U-3D, it was apparent that the Marantz did not have the high frequency extension.  The overall sound and fullness of body with about the same.

I don't think you will get a better HT processor for $1k, especially since you want the latest formats such as 4K HDR and Atmos/DTS:X.  You would have to go to the $2k price point and get a used Anthem AVM 60 to get a faster and higher resolution sound for movies.  I'm not sure that the Anthem

That being said, the Marantz AV7703 is still pretty good for movies.  I think it will be much better than your Emotiva UMC-1.

In my opinion, I would probably slant torwards the Marantz.  The Anthem processors are faster and probably have more exciting high frequency, but I don't think they will sound as natural or as full bodied as the Marantz.
I've heard or had a demo of every one of the aforementioned processors, but the Yamaha CX-A5100 running balanced with Van Damme XKE classic XLR cables bested all of them in clarity and resolution.  This is with all room correction turned off.  I used to be an Anthem fan until I did A/B tests with their top of the line AVM 60.  The anthem sounded dead, flat and lifeless in comparison to the Yamaha.  Other users in the AVSForum thread agreed.  This is with and without ARC enabled, did not make a difference. 

Obviously the CX-A5200 is better than the CX-A5100.  But the OP has a budget of $1k so I believe he can find one used at that price.  They pop up every month or two.  

I do not like what Audyssey, ARC, or YPAO does to my soundstage and my top end. 10 years of trying to love these room correction technologies and wanting to believe the hype perpetuated by online reviewers *shakes fist* ... but yeah no thanks.   I prefer Room Perfect or Dirac, so I use a MiniDSP SHD for my mains and an 88a for my center and surrounds for room correction when running the Yamaha.  Of course, for two channel room correction the Legacy Audio Wavelet crushes any of the aforementioned room correction solutions.  But that's another story.  Hope this helps

Interesting idea, I've never had a Yamaha product. How is the 5200 better than the 5100? On the Yamaha website, they list the 5200 for $2700 and the 5100 for $3k. They seem to have the same features. I'd be a little surprised to find either for 1k used though. That's more in the AVM-60 range I would guess. 
@dbw1 I don't blame you, I'm an audio snob and I usually frown on any most Sound United products.  But after hearing countless demos from Marantz, Denon and the usual suspects...the Yamaha give me the largest soundstage and clarity during the demo.  So I was happy with the purchase for my dedicated HT setups.

The 5200 stepped up to 384kHz/32-bit ESS Sabre Pro DACs, and added redesigned power transformer.  It also incorporated a new surround sound feature called Surround AI that optimizes surround effects in real time.  Many of the top receivers and processors from Japan have a of gimmicky surround features I would never use, but I actually found Yamaha's Surround AI pleasant and useful.  For HT use, you can't go wrong.  And of course the bypass mode is always there if you want to play with higher end gear through the processor without altering the signal.  Although a dedicated 2-channel preamps is always preferred.  Obviously my dedicated MicroZOTL and Legacy Wavelet preamps sound considerably better, but it's still a useful feature on the Yamaha that lends itself to experimentation and swapping gear.

@alexbpm Regarding your thoughts on the 5200, I'm considering this as a replacement for a NAD T787 along with a Legacy IV-5 amp.  I have plans for a wavelet processor in the future but this is step 1.  What are your thoughts on the 5200 from a 2 channel listening point of view? I'm using Legacy Silhouette for my front L/R, Legacy Foundation sub, and a Bluesound Node 2i for streaming.   Thank you fro your thoughts on this.