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.