Honest question about cartridge vs. turntable performance.

The turntable can make a large difference. I just upgraded from my old Rega Planar 2 to a Technics SL1210GR. I’ve kept the same cartridge and everything else is the same also. So much less surface noise and overall cleaner sound.

Right, because Rega is an awful overpriced belt-drive turntable.

Your GR has a coreless Direct Drive motor, heavy cabinet, excellent and fully adjustable tonearm with detachable headshell and all this just for $1700.

How you can upgrade your cartridge on Technics and the difference will be huge compared to the difference you have noticed between belt drive TT and proper DD.

tubelvr1, the characteristic that is most noticeable in turntables is noise either self generated or from the environment. Most modern turntables have reasonable speed stability. The way the cartridge performs is determined by the tonearm. The tonearm has to be the right mass for the cartridge and it must give the cartridge only two degrees of freedom, up and down, side to side. Any other freedom particularly torsional is bad. There are other fine points of tonearm design that are also important. The way the anti skate is set up. It should decrease as the tonearm moves towards the center of the record. A neutral balance arm is always best. Most arms are Static balance which is worse. You can tell right away what an arm is. Defeat the anti skate and put the stylus guard on. Balance the arm so it stays perfectly horizontal then lift the head shell up an inch and let go. A neutral balance arm will stay there and inch up. A static balance arm will bounce up and down eventually finding the balance point. 
Will you hear a difference? Depends on your system and how critical you are. There is definitely a point of diminishing returns. Get a SOTA Sapphire. Put an Origin Live Enterprise arm on it and you are 95% of the way to the best turntable made. Whatever that is:)

Mijo, I don’t disagree with your general principles, except as regards the prime importance of speed constancy, which I emphasize more than you, apparently.  But then you come down to recommending the Star Sapphire, a spring suspended belt drive. I owned one for 10 years as my only turntable. At the time, I considered it an entry into the high end of Audio. I ran a triplanar tonearm on it, for most of that time. I only later realized that vinyl reproduction does not have to include unstable piano and violin notes and muddy bass, which is all I ever got from the Sapphire. I went from the Sapphire to a Nottingham analog hyperspace turntable, also belt drive. It was far superior in all ways, especially after I added a Walker motor control, using the very same triplanar tonearm. I just think the sapphire is not a good choice for a paradigm. I do not mean by this to demean all of the Sota turntables. As I understand it, they have made some major improvements since the sapphire was their flag ship product.

the other thing not mentioned here is the phono preamp... you can't go cheap on that... plan on spending at least $500. If you are using anintegrated unit with an inexpensive phono pre, start there or you could nothear much of a difference in upgrading a TT.

Lewm, that would go against every review ever done on the Sapphire and my own personal experience. Getting a Triplanar on there must have been a lot of fun. I would have to assume something was wrong with your table. I have never been next to the Nottingham. It reminds me of the Brinkman Balance. At any rate I prefer suspended tables. You can make a decent improvement on your Nottingham's performance if you put it on a MinusK platform.    https://www.minusk.com/products/ct2-ultra-thin-low-height-vibration-isolation-platform.html?hm