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@everettT
Hmm, I won't be so sure. It's an older model and may or may not properly support 4k, especially 4k DRM which require HDCP 2.2 which comes with HDMI 2.0. I didn't see anywhere on specs that it supports it.
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@Dolby atmaz
Since you're provides measurements in meters, I assume that you're from wrong side of the atlantic and I won't able to directly link to most US based online stores. What I would recommend to look for 2017 AVR models (with HDMI 2.0/HDCP 2.2 mentioned in spec sheet) for sale maybe even you'd get lucky with someone selling last year model second hand.
Short version, I fully expect you'd be having issues with 4k content like Ultra Blurays and Yamaha RX-V377 avr.
This HK 5.1 speakers system (or as we call it HTS - home theater system) is meant for much smaller spaces than you have now. 40 sq meters thats 430 sq ft or about 4300 cuft and puts you squarely in Large room category. (
https://www.audioholics.com/loudspeaker-design/subwoofer-room-size)
I understand that the budget for upgrades is not there yet, but I strongly recommend to adjust your expectations for your system in that large room much lower.
One trick which may help you a bit is to place the sub in the closest corner to your seating position