i have the 207 and the 507 and the sound difference is not so great but more of a balanced" right" feeling to violins as the upper high frequencies are'nt clipped there not  as compressed.comfort is better with the steel headband and leather cups and steel fork yokes holding the drive units are...

i have a 323s modded with larger smoothing caps(panasonic 370uf400v fit straight in bypassed with 630v.1uf polys) and the alps 50k removed and replaced with a stepped attenuator DACT ct2-50k-2 and it is sublime with SR 507's.The 323 is perfect to my ears and it was easy to do apart from...

for what its worth i pulled the alps 50k pot out and fitted a chinese dale/vishay stepped ladder attenuator costing $30 fitted with ko-on resistors and transformed everything about the srm323s's reputation if only Stax fitted them as standard!.Suppose the company would not have an upgrade ladder