Just curious what speakers you will be using. Both amps will be great. It just depends on what you are looking for in your final voicing. I actually think the MXR-20 balanced with the Ref 6 could be an awesome combo. The Ref 6 will wake up the MXR-20 and I don’t mean that in any negative way. If you have heard both amps, you’d easily understand my comment. ARC and Pass Labs have traditionally been paired together with great success. But my previous experience pushes me towards ARC and Ayre.
ps, Ayre is not crazy about driving difficult speaker loads so please keep that in mind.