There was no indication as to the characteristics desired from this upgrade. That knowledge would have helped tailor a response. Still, several good suggestions have already been made. To expound on a couple of them, the Sonic Frontiers Line 1 is more neutral and analytical sounding in its stock form. It's the most "solid state sounding" pre- I've heard. Adding the right NOS tubes does warm things up a bit, but it's not going to give a highly "tubey" sound. On the other hand the Rouge 66 has more more classic tube characteristics.
In this case, knowing the 3B-ST's analytic (dry?) leanings, on paper I'd give the edge to the Rogue. To borrow someone else's analogy, it's a yin-yang combination that helps avoid too much of a good thing.
The usual disclaimer applies: I haven't tried these pairings, so where possible please listen before buying. BTW, I own a Line 1 (which is a yin-yang compliment to my McCormack amp) and have also extensively auditioned the Bryston, though not together.
In this case, knowing the 3B-ST's analytic (dry?) leanings, on paper I'd give the edge to the Rogue. To borrow someone else's analogy, it's a yin-yang combination that helps avoid too much of a good thing.
The usual disclaimer applies: I haven't tried these pairings, so where possible please listen before buying. BTW, I own a Line 1 (which is a yin-yang compliment to my McCormack amp) and have also extensively auditioned the Bryston, though not together.