I have an SWR Stereo 800 powering my DB 680 based rack. It is totally killer. I honestly think you'll be fine with any quality power amp. If I were you, I'd keep using your Bergantino as a power section and put the 680 in a small rack. Then you can bring the pre or leave it home depending on the gig and sound good no matter what. I recently acquired a Noble which I'm running into the power section of a TecAmp Puma. It sounds 92% as good as my big rack and is a million times more convenient.