I now have about five hours on Claritycap MR in Merlin mid/woofer section, replacing stock cryoed Hovland. This covers 2200hz down to low 30s in one driver. This was a big step up-- and a reminder that midrange and LF is where the music lives. The stage opened wide and deep, dynamics are full of energy with underlying calm, and instruments and voices sound more natural.
Having already completed coupling cap upgrades in phono section, line stage, Merlin BBAM equalizer, and amp(using V-Cap TFTF and Mundorf Silver/Gold in about equal measure), I'm coming around to Duelund's viewpoint that the speaker crossover is perhaps the most important target for a signal cap upgrade.