The Threshold SA4e input impedance is only 600 ohms in balanced mode. If you want to run balanced you will most likely need a ss pre. I can't speak for the MW, but the ARC would have to used in single ended mode. It wouldn't be able to properly drive the 4e in balanced mode.
Preamplifier for Threshold 400A
HI members. I need some advise on choosing a good preamplifier for a Threshold 400A. At this moment I'm using a Blue circle Despina 3 Preamp I would like something that offer balance inputs for future upgrades to a Threshold SA 4e. Your advise will be highly appreciated. Thanks. Osiris.