I would suggest that you buy as good a cartridge as your Denon/Signet combo is capable of handling, so if you stay with your re-discovered passion you can use it when you upgrade to a new table/arm.
Unfortunately I'm not familiar with your Signet, or with the Sim Moon with respect to the minimum output a cartridge must have to work with it. Since the Lydia (a fine cartridge) is a MC I presume you have checked that it will work.
The modern version of your old Karat is the 17D2 MkII, with .23mv output, 5.3 grams and recommended loading of 100 ohms. I own it - great tracker, fast with excellant detail but not overly bright after it breaks in. Lists for $750.
The Lydia Beta is a bit heavier at 8g, with a higher output of .5mv and the same loading. List is $995.
Don't think you could go wrong with either. If you have a local dealer for either or both, perhaps you can persuade him to let you bring you Denon/Signet in for an in-store test.
Unfortunately I'm not familiar with your Signet, or with the Sim Moon with respect to the minimum output a cartridge must have to work with it. Since the Lydia (a fine cartridge) is a MC I presume you have checked that it will work.
The modern version of your old Karat is the 17D2 MkII, with .23mv output, 5.3 grams and recommended loading of 100 ohms. I own it - great tracker, fast with excellant detail but not overly bright after it breaks in. Lists for $750.
The Lydia Beta is a bit heavier at 8g, with a higher output of .5mv and the same loading. List is $995.
Don't think you could go wrong with either. If you have a local dealer for either or both, perhaps you can persuade him to let you bring you Denon/Signet in for an in-store test.