I try avoiding these conversations but both of these companies have crap service and the ARC GS150 I tried was not that great and for the asking price a flat out ripoff. I had MB185 signatures long ago that couldn’t maintain bias so I moved on from them. Asking which brand is better is a loaded question especially for these forums that seem to bring out the nasties from some of us on these forums. Brands like VAC, Quick Silver and a few other offer some really good values on the used side for high power tube amplifiers.
