The hallmark of a good preamp is how quiet it is. One of the benefits of capacitors is that they help the preamp from introducing noise into your system.
What's the value in lots of capacitors inside a line stage preamp?
On one system I am using a Conrad Johnson gat2, and it's loaded with Teflon capacitors and step attenuator volume control, vishay, and I'm sure lots of other lovely things going on. It's doing a great job.
But I have no idea how important all those capacitors are except that they store a lot of reserve power and are available to fulfill Power demands of musical changes. Maybe that's all I need to know.