Diminishing returns?


I have a Denon X3700, which I bought primarily for it being within my budget, and capable of handling 8k and HDMI 2.1.  I’m currently in the market for floor standing speakers that will serve a dual purpose as both  2ch audio, and the L/R in a 5.1.

I would imagine at some point, the limitations of the receiver will outweigh the benefits of purchasing higher-end speakers?  In essence I would lack the equipment necessary to truly bring out the best in the speakers.  Is this an incorrect assumption?  Assuming I don’t plan on using anything besides the aforementioned Denon, at what price point would investing in more expensive speakers be pointless?

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"...Sadly, this place is run by 2-ch fanatics (majority of them are deep into Vinyl or should I say anti-digital) Do you see the pattern, they have a one track mind….digital is bad, home theater sucks..."

I think you mean, luckily this place is for two channel enthusiasts. I still have my 60s and 70s LPs but I only listen to digital sources. 
Depends on resolution of your system to determin that point and how much you have to spend.
Ah yes, two-channel 'enthusiasts'. I admit to being one totally, but I still thought to suggested a center and surround solution (with better mains for two-ch use). It seemed to be what was needed per the O.P. unless I misunderstood. Sometimes it's not about what we want I guess.

I remember the days having to work it out for stereo and video in one system (adding TV sound in the 80s to a receiver). It was more challenging as the system grew and eventually separated.  These days I feel very lucky to have individual rooms/setups for high end two-channel audio, regular TV, and a home theater. It just takes time and if the O.P. builds carefully those items are very usable later. (plus I probably never sold a piece of audio gear in my life...)
Keep the Denon and buy speakers you really like. They will sound great (assuming a common sense match).