What do you think about the 160v rating on 22uf caps, enough?
I don't know what voltage the power supply is outputting to the plate circuits of the 12AX7's, but I suspect you should go with a considerably higher rating on the caps than 160V. Perhaps the 12AX7's are being run somewhat lower than 160, but probably not much if anything below 120 or 130V. And the 12AX7 and 12AX7A have rated plate voltage maximum's of 330V, so in the absence of further information it could very well be that they are even being run a bit above 160V.
Good derating practice in my experience as an electronics design engineer (although it was in defense avionics, not audio!) was considered to be a factor of 2 or more. Meaning use capacitors with voltage ratings of 2 or more times the actual voltages that are likely to be encountered; otherwise long-term reliability is degraded.
And, finally, the 450V rating of the existing electrolytics was probably chosen for a reason!
Regards,
-- Al