You really don't gain much by "upgrading" from A30 pro to A90. A30 pro has gobs of power even for balanced cans and way more power than the A90 for unbalanced headphones. Only real reason to upgrade, in my opinion, is if you need the output features of the A90 that aren't available on A30 pro.
Sundara without EQ preference score 92 https://www.dropbox.com/s/o3fza1a4kmmy4vr/Hifiman%20Sundara%20%282020%20revised%20earpads%29.pdf?dl=0
Ananda without EQ preference score 82 https://www.dropbox.com/s/l1wivpf8901uflr/Hifiman%20Ananda.pdf?dl=0
And it's not like the Ananda's...