It this a decent Phono setup?

It appears that you have a pretty well balance vinyl set up. Nothing stands out as a real weakness. If you want to invest a little then you could get a better cartridge.

Longer termed, my rule of thumb is that each component (carefully chosen to be the best in class and compatible with your system and taste) will usually cost about the same. So TT, Phonostage, preamp, amp, DAC, Streamer. This is a useful way of looking at the whole system.

Looking this way, your Mark Levinson sets the level at $3K / component ($3K preamp + $3K amp). Therefore to get the very most out of your system a $3K TT and $3K Phonostage would be optimal. So, if you wanted to look into the future there is room for growth in your vinyl end.

Just a real rough guide. But typically over the last fifty years of upgrades I tend to end up in these proportions + or - 25%.

Sell the Denon. Get a Technics SL1500 TT ($1800) and a Hana SL mc cartridge ($750). Way better sound quality than your present setup. 

I agree with Jason, better turntable,

turntable, I would look for used one on hifi engine, within your budget (stretch it, think long). check reviews of ones that appeal to you, ask here again about specific models, questions to ask sellers

https://www.hifishark.com/search?q=turntable

put your price range in, and to see new listings every morning, sort by

’first seen, new first’. all countries, or change to your country only.

note: to eventually use different cartridges: go for ’standard’ removable headshell, ’standard’ S arm. your existing denon has removable, but it fits it’s specific straight arm

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and better cartridge with advanced stylus shape

https://www.sound-smith.com/articles/stylus-shape-information

I often recommend this cartridge (wide channel separation and tight channel balance, and great sounding

https://www.audio-technica.com/en-us/vm540ml

get rid of the ortofon red.

IF you can match the capacitance, replace it with audio technical vm540ML

for the 540ML, the combined capacitance of the tonearm wire, phono cables and phono stage cannot exceed 200pF. 

Your analogue source components are far out classed by your amp and speakers, and I don't think upgrading any of them is a good use of funds. 

Do you have a budget to improve your front end?

Are you committed to vinyl? I ask because my digital source rivals my vinyl source at about 1/4 the cost.