If you think your system sounds great, why not just stick with it? Keep in mind that if you go with tubes, you may end up going down the "rabbit hole", spending countless hours and dollars looking to get the lowest noise and highest performing tubes. This is coming from a tube guy.
Exactly, even in the line level pre-amp or power amp.
In a phono stage can be more problematic, especially for LOMC cartridges.
If you want a very special phono stage for low impedance LOMC then check Current Mode (Current Injection) type of phono stages like 47 Labs Phono Cube or others.