I agree with Gbart that you're looking for an amp that can double down. You're looking in the right power range, although I don't think there is a specific wattage that will work with the Goldi's, it just depends on the individual amp and how beefy it is.
I also agree with the McCormack suggestion, although I still think that in your price range the big Marsh amps will provide the best bang for the buck.
If you can stretch your budget a little, the Wyred4Sound amps sound like they might fit the bill perfectly, as they've been getting a lot of buzz, although I haven't heard one. Or, sell the preamp and get the Wyred4Sound integrated.
Michael