I have an Aphex 107 manufactured in 1997 with a Phillips 12AT7 tube in it (the original). Any benefit swapping this tube out for another? If so, to what Brand and Type of tube?

It's time for me to invest in a decent mic preamp. I'm looking at The Brick and the Aphex 107 with 12AT7 Tubes installed. I've been reading praise about both around here.

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