Time to play Sherlock Holmes, make notes
Imbalance: Assuming you are right, I would prove it is the cartridge, i.e. rule out other potential problems before I bought a new cartridge: Your phono: you have two sets of interconnects, and a variety of tubes in 2 devices and a specific preamp input that are all different than your digital source.
1. move the digital to the input you are using for your phono pre: still imbalanced, then it’s that input, not .... good, it’s somewhere in the phono chain, where exactly?
2. switch phono l and r, weak moves to the other side, tells you ......
3.
4.
Cartridge re-builders say the MAJORITY of cartridges they receive have had inaccurate anti-skate for years, uneven wear leads to uneven sound: the replacement needs to be right. Who will install/calibrate your new cartridge?
I also like AT MM cartridges with excellent sound and imaging specs (wide channel separation/tight channel balance) replaceable MicroLine stylus which have the largest contact surface, thus longest life and minimize wear on your grooves.
They track at 2.0g, I prefer lighter, and I prefer stiffer cantilever, I risk used vintage cartridges to get beryllium which is no longer used, recently bought two used AT, AT150e and AT160 bodies with ATN160ML stylus which track at 1.25g, each in your budget, but buying used cartridges is not for most people I know.