Hi Tom,
The MRs are quite an improvement on the ESAs, due to the unique design features of the former, in terms of addressing the issue of mechanical resonances. The white paper written on the subject makes interesting reading:
http://www.hificollective.co.uk/pdf/claritycapmr.pdf
I've compared the MRs against the ESAs, and there is no question that the former offer a significant sonic improvement. If you can get the right values in MRs, then you've got a nice upgrade waiting there, should you wish to pursue it
Marco.