Help me choose a mono cartridge


Hi all.

I just got myself a Black Friday gift. The Beatles in mono box set at a very affordable price on Amazon.

I do not have a mono cartridge but would like to get one to take the full sonic advantage of this box set. I do not have very many mono records. Approx. 50 out of a collection of 2000 lp's.
Which mono cartridge would you recommend in the $500.00-$800.00 range new or used.

My analog front end consist of:

Sota Cosmos IV with Graham Phantom II
Stereo cartridges are Ortofon A90 and Dynavector XV1's
Audio Research REF3 LE with GNSC reference mods
Audio Research REF 2 Phono (not SE version) with GNSC reference mods

Any recommendation much appreciated.
Thank You.

smoffatt
lewm - - Sorry if I was unclear in my post:  I said I was thinking of replacing the Helikon mono with an Ortofon mono but wasn't sure which one would be best.  I would not go with the 2M but am looking at either the Cadenza or Quintet. Or . . . perhaps I should get the Helikon repaired.

Trying to get a handle on conical vs elliptical vs fine line and match all that up with my mono collection (1950's originals up to current reissues) is a bit daunting.  Then there's the "best bang for the buck" angle to take into account.  


I agree that all those are issues associated with choosing a mono cartridge or even just choosing to buy one at all.
I finally decided on a new mono cartridge:  ordered an Ortofon Cadenza  mono from Needle Doctor.  They're giving me a $320.00 trade-in credit on an old, worn out Ortofon Jubilee, so the net price for the new cartridge is $960.00.  I'm looking forward to its arrival.
Hi all.
Since i have a somewhat limited budget now that i am retired, i have decided to go with an Ortofon Quintet mono (white body). I ordered it thru a dealer in Montreal for $540.00cnd but the distributor in Canada is out of stock and the factory in Denmark is shut down for the Holiday Seasons. I should get it by mid-February or so. Love the sound of my Beatles mono set thru my REF3 with mono switch but i just can't wait to hear the same set with a true mono cartridge. 
Happy New Year to all.

Smoffat, Please do report your results here.  Specifically, how does the Quintet mono cartridge compare to using just the mono switch?  And do you perceive an additive or synergistic effect for the better, if you use both?  Those observations would be very helpful.  From my reading and searching, I was unable to verify that the Quintet mono has been built such that it does not produce a signal in response to vertical modulation of the stylus, but neither can I say that it was not.