What is the "best" cartridge a Technics 1210...

Stanton 680 EL
Ortophon Nightclub E

I wonder if anyone has tried even higher-end MC carts with the Technics -- stuff in the >$1K range from Benz, Koetsu, Lyra, ZYX, Sumiko, etc. I know it =seems= like a mismatch from a price standpoint, but is it really?

I know a guy that runs his M5G with a Dyna XV-1s and thinks its an outstanding table, he also has a top flight phono stage.

I was considering Denon DL-301 MK2 after reading a lot of good reviews. My question is, what about the headshell. I would like to update the stock headshell, buton technics tonearm it has 12g effective tonearm mass. And all the good headshells I see are 12g, so a little math:
(12-7.5+12) = 16.5g - effective tonearm mass with the new headshell.
where:
-7.5 stock technics headshell
12 - new headshell

And this will move the resonanse to a point, where it's not good, right?

Do you guys have any suggestion for a good headshell, that will sound better than the stock one?

First you have to convert Denon’s (DL-301 MK2) compliance from 100Hz (Japanese only system) to 10Hz (Western world system):

Compliance of your Denon is 13x 10-6cm/dyne @ 100 Hz
You have to multiply it roughly on 1,7 to find out what is the real compliance of your cartridge @ 10 Hz

13 x 1.7 = 22,1 cu - this is real compliance of your cartridge.

Then you have to count not only effective mass of the tonearm + headshel (which is 12g as you said), but the mass of the cartridge itself (which is 6g). You have to count in the lead wires weight and screws/nuts weight too.

Then USE THIS ortofon diagram to calculate resonance frequency.

You can also use Hi-Fi Test LP to calculate resonance frequensy by playin this record with your actual cartridge/tonearm.

As you can see the resonant frequency with stock headshell and your Denon will be around 8Hz (roughly). Resonance frequency within 7-12Hz is optimal for the system! Technics stock headshell is a good one if you have already replaced stock headshell lead wires. Before upgrading the stock shell you have to completely rewire your technics with Discovery Tonearm Wire (internally) and with external RCA phono cable of your choise. 

I think you need lighter headshell, not heavier if you are so concerned about resonance frequency with this tonearm/cartridge combo. Or you can simply ignore this theoretical point of view if you play flat (not warped) records with heavier headshell.

P.S. I have 8.4g DENON headshell for sale here. You can also try the Orsonic lightweight headshell.