Cartridge or Pre Amp

I recently picked up the Pro-Ject Tube Box DS and I am tickled pink on how warm and yet dynamic it remains. I’ve noticed that there seems to be some front stage darkness on some older records. Nothing more volume can’t fix. Would upgrading my AT-ML150 cartridge or the pre amp would this phenomenon or it simply a characteristic of the production and pressing of its day?

My setup:

Technics MK1200 MKII various upgradeds: wires, tonearm, etc.
AT-AL150/OCC Cartidge
Pro-Ject Tube Box DS
Bryston 4B3
Bryston Model T speakers
Simaudio MOON NEO Preamp
OPPO UDP-205