SOTA Cosmos and other models - lean sounding?

Montaldo, I have owned SOTA tables since 1981. I currently have a Cosmos with a 4 Point 9 on it.
To answer your questions,
#1 Absolutely not.
#2 No way to account. Too many variables. Bad system, bad ears, who knows. Put the two tables on the same system with identical arms and cartridges and 99.9% would never hear the difference. 
#3 None
Your Sapphire is pretty recent so you should be able to apply all the new upgrades including the DC motor and drive and the new magnetic bearing. Call SOTA with your serial number in hand and ask. If your current table is in good shape just let SOTA rebuild it to current spec. It is just like getting a new table.

Mike

I thought my Lenco idler drive refurbished by Jean Nantais sounded noticeably fuller than the Cosmos IV that I also owned.

Thanks for the great feedback, all! Also pondering a used Basis Debut or an EAT turntables as alternatives to my SOTA. Any opinions are welcome.
It would be psychologically challenging for me to move away from the vacuum hold down, now that I have had it. Not certain of the sonic impact.

Since you like your SOTA, it's a probably good idea to stick with them, especially with the current upgrades offered. I bought a Clearaudio Innovation and learned the hard way just how much the SOTA suspension system made up from my bad rack & floor setup - got to keep that in mind. Now a lot of money later into a high-end rack, the Clearaudio is awesome. But I still keep my SOTA for the Stax headphone rig. No fancy rack needed with a SOTA. 

1+ mulveling. People who use idler wheel turntables either don't like bass or don't have subwoofers. They all rumble like express trains. They are why rumble filters were invented in the first place!
montaldo, we all get that urge for a change. It is that urge that has led me down the path of destruction on several occasions. Stick with what works.
All good turntables, those that do not add to or transfer anything to the process of reading a groove sound the same. Those that sound different in any way are adding something that should not be there whether it sounds euphoric or not. 
As an aside. I have a 192/24 copy of Dylan's Desire and the MoFi 45 RPM version. We sinced them up and on first listening all three of us there at the time thought the vinyl sounded better. The vinyl had this glow for lack of a better term and it made Dylan sound as if he were standing out there at some distance. The digital version sounded as if Dylan was standing right in front of you singing into a microphone and on closer inspection the digital was more detailed, the violin in Hurricane had more rosin to it. So like Nelsen Pass's amplifiers the vinyl is adding something to the process we like. Nelson is right when he says audiophiles don't care about accuracy. They just want to be happy. I think I just contradicted myself.