There's a Pass Labs x2.5 that I'd think would be a significant improvement in your system and is under $1500. I'd put this in the "you just can't go wrong with this" category given your price range and goals.
However, since you're also open to ideas on the tube front, for $2k (or maybe less with a metal case) you can have Don Sachs build you one of his SP14 preamps. If you call him and discuss your setup and needs he'll probably give you some good thoughts, and as a big bonus I believe you have a short trial period so little risk involved. This is what I'd do as this could potentially get you to the "truly special" product category, so I'd encourage you to at least give Don a call (no association BTW). Hey, it's free. Anyway, best of luck in your quest.
However, since you're also open to ideas on the tube front, for $2k (or maybe less with a metal case) you can have Don Sachs build you one of his SP14 preamps. If you call him and discuss your setup and needs he'll probably give you some good thoughts, and as a big bonus I believe you have a short trial period so little risk involved. This is what I'd do as this could potentially get you to the "truly special" product category, so I'd encourage you to at least give Don a call (no association BTW). Hey, it's free. Anyway, best of luck in your quest.