contact Tboooe. he had both preamps. I am sure he wouldn't mind sharing his thoughts. REF3 is a good preamp and I think if you are listening to a lot of large scale orchstral it may serve you well. Tboooe kept MBL. But I believe his taste in music is small ansamble jazz and vocals and not a lot of large scale classical. But do contact him. Also read through his system page he shares his thoughts there in regards to both units.
Best of luck!
Best of luck!