Cartridge upgrade for $600

Which MF? How much gain in the phono stage? What input impedance values are available on the phono inputs?

Without knowing those specs any MC cartridge recommendation would be about as useful as recommending tires without knowing what car they're for or where it will be driven.

Musical Fidelity A3.2 Intergrated with phono:
Input sensitivity: 250mV (line); 2.5mV (MM phono), 350µV (MC phono). Input impedance: 220k ohms (line); 47k ohms (phono). Overload margin: 26dB (line); 24dB (phono). Channel separation: >70dB, typical.

In that price range, I would suggest you consider remaining in the MM or MI domain. Low end MC cartridges are not necessarily going to be superior to any of the better ones. You could just move up the Ortofon line or consider a Sound Smith MI cartridge that meets your price limits. There are literally dozens of good choices available to you.

Among great-performing MM/MI carts at $400-600 are the Audio Technica AT150MLX (TAS's Cartridge of the Year), Ortofon 2M Black, Grado Reference Platinum or Sonata, something from Goldring or one of the MM Clearaudio wood bodies.

I have had and loved the AT150MLX for the past 4 years. It has nice detail without beating you over the head with it, and a lovely top-to-bottom linearity and coherence. Great tracker too. Often selling for $499, you can find it for around $318 if you look around. You must load its capacitance at between 100-200 pF. Mine sings at 150 pF.

One day you are thinking of trying a different Integrated amp and now you are looking at cartridges ?

Whatever you decide to do , make it worth while , even if you have to save more money to do so....as right now it seems that you have some money just burning a whole in your pocket.