Why don't you want to stay with MF? I run my ESL 989s with a MF NuVista M300 integrated. It sounds marvellous. I was stunned by how loud the Quads play with this amp - I have so far not managed to trigger the safety switch on the Quads - and i have played at levels beyond what i found reasonable...
The MF is stable enough to deal with any impedance problem, so no need to tube magic...
The MF is stable enough to deal with any impedance problem, so no need to tube magic...