What's the best balanced pre $2000?

I have pair of active speakers that are dead accurate but a little sterile. Thinking of a tubed pre to add a little melifluous magic but maintaining or enhancing the detail and sound stage. The feed is balanced so a balanced pre would be best although RCA to XLR is doable. I'm also open to an older unit that would benefit from a cap upgrade. I'm thinking an Audio Research unit but any suggestions within this brand or outside would be appreciated.