How do you know that the caps are the problem? I know that I recommended the Bat, but sometimes things don't work out. I was kind of surprised that it didn't sound good for you. The last thing I would recommend for you to do is put money into an expensive preamp that you've never heard sounding good. There's other choices, and not only that, you really don't know if there is anything wrong with it.
That said, if you want to look into Caps, I would contact Bat. They're known for offering Cap upgrades, and if you explain to them the problem, they may be able to give you some good advice. Bat does have a very good reputation. I don't think they would mislead you in any way just to sell a preamp.
