Upgrading Sonic Frontiers Line 3SE to ???

The Line 3 is certainly not shy in bass and dynamics. I've heard tighter bass but I would look more at the amp/speakers. Have you tried tube rolling?

Have you tried a different amp to see if that makes a positive difference in your system? I'm using a Line 3SE and don't have issues with dynamics and bass weigth, but I've got Bryston 7B-STs so there's plenty of bass drive.

the 3se is one of the finest pre's ever. the bass issue u are you have is more likely one of the room, the amp, or your speakers. you can pend more on a pre, but most likely you will just get different, and not better.

I did bring my Line 3SE to a friend's house for A/B in the past, his ARC Ref 2 Mk II outgun my Line 3SE on bass weight and dynamic for sure. I later found out the 6GH8 was worn and replaced them, that restored some of the dynamic but 6H30 pre (ARC Ref 2 Mk II or BAT 51SE) do have an edge on dynamic from what I read/heard.

Currently I have Sylvania 6GH8, Siemen 6922, and Sovtek 6H23 in buffer. I have plenty of Valvo and Tunsgram to put in buffer after 6H23 are worn. What will be a good choice for driver without costing a fortune. Don't have $500 to spend on a pair of pinch waist, but can swing $250 for a pair good tubes if that will improves the bass.

I tried many amps in the past, but only BAT 75SE gave me the goosebump I was looking for. For sure 75SE does not have solid state like bass and that's the reason of 2nd amp like Pass, but I like the amp enough I am willing to search for a new pre to go with it.

Amperex A-Frame 6DJ8 in the buffer should help you achieve the dynamics/bass weight you are looking for.