Cary 805C

i like to mod this pair, help what i can mod on this amps
i am thinking replace caps, if so please help me what kind and which one need to upgrade.

thanks in advance
Re-capping this amp with Mundorf MCap® Supreme Silver & Gold & Oil will bring this amp to an entirely different level. Some like the Mundorf modded 805C over the 805AE.
which caps or all the caps ?
Replace ALL of the caps.
I believe Brf meant all of the coupling caps, not power supply caps.

Mundorf Silver caps are designed for coupling and speaker crossover duty, not power supplies...they would become too bulky and expensive.

Coupling caps are tipically .1uF to 1 uF, 400 or 630 Volts and are connected between plate of the first tube to grid of second tube and so on.
I believe your amps have one cap between first 6sn7 and second 6sn7, another one between second 6sn7 and 300B, one large cap between 300B and output tube.
Good luck