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.
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.