Honest question about cartridge vs. turntable performance.

I agree with chakster regarding the newer Technics.  The older Luxmans I am sure are fantastic.  My friend has an older Luxman but he cannot get it repaired anywhere locally so that is why i would not take my chances on one.  If I had skilled technicians locally that could fix it without sending it out for repair I would definitely consider one of them.

Chakster, I definitely do not have to own one. I suspect I have had very close contact to more of them than you unless you have similar experience. It is not my fault you drink the Kool Aid. 
Do yourself a favor. Contact Hideaki Nishikawa here,   https://techdas.jp/pages/contact-techdas/ and ask him why he did not use a direct drive system. You can come back and give us his answer!

I would say given the choice I would put a superior cartridge on an inferior turntable.  

Mijo, While you were going to medical school in or around Miami, I was going to medical school in NYC.  Lyric Hi-Fi and Mike Kaye were in their heyday at that time, and I hung around that store and a few others, like Harmony House on 72nd St all too often.  (Being a medical student in an MD/PhD program per se was taking up all my other time, so I did not work in a store.) Mike was a very nice guy, would talk about audio even to a poor medical student.  I bought my first pair of audiophile speakers from him, IMF Studios.  I wanted the Monitors but could not afford them or fit them in our tiny apartment. Later on, Mike took a back seat and the store became snotty, you needed an appointment to get in to one of their listening rooms.Still, in your interesting narrative of your early years, you did not actually name any of the actual DD turntables you were hearing back in the 70s. I might note that those relatively early DD turntables in general did not reference the speed to a quartz oscillator; that came along in the early 80s.  I would not mess with any DD lacking a quartz referenced servo, and it's no wonder you were not impressed with those early efforts at DD.  The difference between the original Technics SP10 and the SP10 Mk2 is the incorporation of a quartz reference for better speed control in the latter case.  However, the SP10 Mk2 is one of a few DDs I have owned and heard that really do have a coloration, in my opinion.  I owned two Mk2s; they added a faint "gray"-ish coloration that was only evident when you compared it to something else that lacked that same coloration.  Many others who do not like DD ascribe this coloration to "hunting" due to the servo mechanism constantly correcting speed.  My investigations tell me it is more likely due to EMI, as you mention.  A little shielding added can fix that.  The SP10 MK3 or the new SP10R are rock solid neutral and constant in speed in a way that no other turntable does it. The huge platter of the Mk3 provides inches of shielding from its motor. Another fix in relation to speed hunting is to stabilize the stators on the motor, as done by Richard Krebs.  The torque of the motor while rotating the platter applies an equal and opposite force to the structural elements that restrain stator motion.  If the structure is weak, the stator will move counter to the rotation of the platter by a tiny amount (Newton's Third Law), but this is enough to signal the servo that there is a speed error, so the servo tries to compensate by accelerating the platter, and there you go.  These are issues with modern DD (and also with belt-drive motors where the consequences of counter-force are different), but for me the issues with belt-drive are audibly worse, so I've made my choice.  You consistently mention the Grand Prix Monaco.  There are many things I like about that turntable but it is off my list due to its light weight and carbon fiber construction, perhaps unfairly on my part.  Even I would tell you, you are better off with a Dohmann Helix belt drive. I favor mass over a suspension, unless you are talking about Minus K or Herzan (which I think makes Minus K under another brand).  Mass is needed to counter the force of the motor, again the motor wants to turn the plinth or the platter, and it doesn't care which. If you want a heavy platter (and I do), you need a very massive plinth, which also, if properly designed to incorporate constrained layer damping, soak up resonance.  My SP10 Mk3 sits in a 90-lb plinth I made or had made out of slate and cherry wood.  The Kenwood L07D was conceived with a 60-lb plinth made of a hard particulate of some kind plus a hard wood, for CLD.

As to the Rega, I disagree with Chakster's dismissing them out of hand.  I think the higher end Rega turntables are very interesting experiments in extreme rigidity with low mass, and I'd like to hear one some time. Maybe they are bang for buck contenders in belt drive world.

Guys (or gals) the original question posed was not belt versus direct. One technology is not better than the other. It depends on the table. Some manufacturers make both types. OP is talking about going from a good basic turntable to something better or upgrading a cartridge. 

From my experience, the arm is most important (but I don't have experience as Mike Lavigne from bottom to very top of the market). It must be matched to the table. However, you want to look at resale value down the road. As someone who faced this type of decision, it is hard to sell a tonearm standalone and people like to buy known quantities. Years ago I had an MMF 5.1 and wanted an improvement. I was about to buy an arm, but was able to get a new table with the same arm for almost the same price (Rega, known fro their arm's high value). If I sold the MMF with a better arm, it would not have added the same resale value as the new table. All you Rega haters just please relax (especially Chakster). When I upgraded the Rega it was easy to sell in pieces because I upgraded the arm first (huge improvement) and then matched it to a table that cost about 80% more than the arm upgrade (minor improvement). I think up to $5K or so, get a table with an arm to match. So a table upgrade (with arm included) will yield better results than a cartridge.Then you can look at more complicated decisions.

Cartridge, as Mike Lavigne said is disposable. I wouldn't spend more than $1K, but that is me. Second most important is phono stage, which is not spoken about much, as one of the 4 main components. Not talking about Linn that breaks it down into a million pieces.

So, I guess cartridge is 4th, assuming your table is at the right speed with minimal rumble (sometimes a bd assumption). Also, you need to look at your budget. The question is how do I get the best improvement in SQ for my buck from a given investment. That is critical, otherwise you can go down a rabbit hole of upgraditis since there is ALWAYS something better of everything. Figure out your budget and go from there. Significant improvements cost significant dollars and the more you spend the more you have to spend to get noticeable improvement.

For a grand or two, I'd get a new table/arm. Then a new phono stage. Then cartridge to match the phono stage, assuming you are happy with your speakers and cables (oh no....you're going down the hole....)