I have owned both Anthem and Marantz. Currently using Marantz. There are not a lot of reviews on the 1140, but I am fairly confident that the 8015 and the 1140 would sound very comparable. The issues you are going to run into with Anthem are a few things.
1. Anthem will not support HDMI 2.1 out of the box, you must upgrade down the road for $$
2. The both use the same AK4458VN DAC
3. If you are going to upgrade a to 15.2 Speaker config (god bless you
) the Anthem supports it
4. I have not used ARC room correction on the Anthem since back in the AVM50 days, but it did do the job well
5. As a Paradigm/former Anthem owner (Same Company) I rate their customer service significantly better than Marantz based on my personal experience
6. ARC room correction on the Anthem was buggy at launch and delayed.
That brief analysis, there is still many more things to consider. If I had to make a decision today I would go with the Marantz. I am not going to buy an 1140 only to pay $500+ to upgrade the HDMI down the road. The Marantz is already the less expensive unit. You may also want to consider the Denon 8500. Otherwise if you are set on Anthem I would wait until the fully upgrade the HDMI 8K 2.3 before you buy.