preamp tubes

I currently run an MFA Magus C preamp, modified and hot rodded by the designer, Scott Frankland. I am the original owner, use it at least a couple of hours every day, and love the sound.

I'm toying with the idea of replacing the tubes: 2x 12AX7, 1x 12AT7, 1x 6DJ8.

I am wondering:

Hey guys, I'm relatively new to the forum. I want to get better at recording, so I'm focusing on adding gear to round out my studio. Here's what I'm working with right now-

6SN7 & 12SN7. any of you guys who build or tinker have any opinions?

I know the au,at & 6sn7 are lower gain than their counterparts.

Any thoughts on the way they sound?

Thanks