Just replaced stock 12AU7 with a Siemens 12AU7 ECC82 Silver Plate Tube. Change was a pretty big positive. Like the detail and actually believe low end is a little better as well.
The BRIMAR CV4004 pair were a positive change as well to answer my own question

Still thinking about changes for the 5Y3GT and OA3 possibly. Really liking what has been done so far.