Is a turntable upgrade a fool’s errand?

Yes this is a valid assumption. But this assumes that there will be enough of an improvement in the sound quality of the source for the consequent heard improvement via Sonos to be worth the spend to get it and, seeing that the TT is a source, to maintain it.

That underlying assumption may well not be valid and needs to be tested.

@rmms78

Imho that is, as most vinyl topics are, a very subjective experience. The Sonos build in AD converters are quite good and a better analogue input in most cases will result in a better output on the speaker. 
But… for a turntable of that class I would recommend a least a setup like Sonos Five (in best case two as a stereo setup). But also that is a very individual decision and maybe a stereo setup of Era speakers also would fit for you. 

While better quality signal entering your Sonos system will improve the quality of your sound, the Sonos ADC is a limiting factor. It has been some time since I have done a comparison, but my general recommendation, from previous listening, has been to not spend over $500-600 USD on a turntable if it will only be used with Sonos. A Fluance RT85N at $499 and a Schiit Mani 2 at $149, would push that range, but I think it would be a great sounding combination. I don't think there would be any benefit to spend more than that if Sonos is the only system this would be played on.

You really can’t just upgrade a turntable, it is a system with multiple components and must be looked at that way.

Starting off with the base, it pretty much is there to spin the album and support the tone arm. More precise speed (if you can hear current speed issues) would be an improvement. Also bearing noise (if you can hear it now) could be improved. Last the support could be improved (if you can hear issues there) with more damping of sounds transmitted through the legs and by vibrations in the air.

The tone arm is another complex bit, tracking/anti-skating, tracking force, tracking angles, both horizontal and vertical might be improved (if you can hear an audible impact now) as could be issues with the bearings (horizontal and vertical) adding noise (if you can hear it) now. Mass will impact the arm’s ability to absorb record warps with minimal sonoc impact too, less is better. Last would be vibration damping and resonance issues that could be improved (if you can hear any) now.

The cartridge is a whole book all by its self, stylus shape, MM or MC, impedance and capacitance, tracking angles and weights. Ability to minimize noise added by record surface warping. Frequency response curves (in conjunction with your chosen pre-amp) are important too.

About as much fun as the cartridge is the pre-amp. The basic MM, MC, or both to start with. Then noise, accuracy of the RIAA curves and overall signal quality. Of course you also have to consider the various technologies and the sonic impacts of each, the good news at the higher end the differences should be minimal.

It really comes down to: Are the problems you hear now bad enough that it is worth what it would cost to fix them. For a truly high end solution a $30,000.00 budget would be reasonable.

For something you couldn’t hear anything wrong with $5,000.00 would be the higher end of the range $2,500.00 would be really good gear. 

I’d bet with careful reading of the specifications and not getting features that don’t contribute directly to sound quality you could be happy with a $1,000.00 setup and likely in a perfect listening environment hear the differences from your Audio Technica LP60.

Consider the differences in these two similar turntables and the price difference, double, add in ‘would you hear the differences’ and see where your ears versus budget is taking you.

https://www.crutchfield.com/p_1331200G2S/Technics-SL-1200GR2-Silver.html?tp=75887

https://www.crutchfield.com/p_133GS1200S/Technics-SL-1200G-Grand-Class-Silver.html

FYI my last turntable was an older but similar Technics, a small collection of stylus and I used my very good quality pre-amplifier's phono input instead of an external phono preamp.

I was looking through all the turntable tabs I had open and found just what you need if your lotto ticket hits this weekend.

Just under $300,000.00 but maybe you could get free shipping?

https://www.avluxurygroup.com/thorens-new-reference-turntable.html

Seriously though the description there is a good read when you are thinking of buying something, even at a far lower cost, as the things it does well you want done as well as you can afford too.

Thanks for all of the feedback everyone! Fluance has a pretty good return policy so I think I’m going to go with the middle ground and check out the $300 RT81+ with the built-in preamp. This will allow me to do a little bit of testing to see if there’s any perceivable difference vs the AT-LP60. I love my Sonos system but I think spending $650 on the RT85N/Schiit Mani 2 would be overkill. My consumerist need to upgrade would be satisfied but beyond that I don’t think it would offer much with a Sonos-only output. And furthermore, I have no interest in learning about preamps :-)