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
Rshak, I was interested to read that you contemplate replacing a Helikon Mono with a 2M Mono SE Ortofon.  Would you care to amplify on the rationale for that?  I ask only because the Helikon Mono is much more expensive and has been highly praised. 
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.