Well, unfortunately, this projector won't work with 4K which requires the use of HDMI 2.0 and HDCP 2.2. This has only come out in receivers over the last few years. In fact, HDMI 1.4 has been out for a number of years which replaced HDMI 1.3a.

I'm seeing this receiver as being reviewed in 2008, which puts it in excess of a decade old.

*sigh*

Used gear is not the way to go in almost all cases if you are looking to pair it with the latest technology. It will give you more headaches than it's worth. Yes, it's a deal, but you will be stuck with all that the product offers.

In this case, you will be locked at a maximum resolution of 1080p. Even then, it looks like the receiver only passes the resolution through.

Not sure what you paid, but you should check out Accessories4Less.com and some of their deals if your budget allows it. They have a number of receivers which are just a few hundred bucks and fully support HDMI 2.0.