His amps are now getting on the low side (20-26db) of what used to be normal gain (28-32db).
Doing this he can utilise more of the gain that preamps have to offer, and maybe leave a gain stage out of the amp/s now.
This is good as the s/n ratio will be better, and your not throwing away the gain from the preamps.
Down side is, passive volume controls maybe won’t have enough volume for them, unless the source has more that the customary 2v output.
Cheers George