Rotel RB-980BX and RC-995 upgrade

Hi
I read forum for a while and notice you have expierience with Rotel .
I have 2 pieces from that Company .
Power Amp RB-980BX
And Preamp RC-995
I have aquired them few months ago and they are in working order however sometimes channel play unevenly and power amp gets very hot. I have cleaned pots and selector desoldered of the board dissmantle and cleaned as well as relays in pre.
However in order to improve on the equipment i would like to recap them as a prevention .
Basically i would like to ask you for help with capacitors selection and perhaps a suggestion as what else may need attention . Its all still original black gate. Perhaps i should just do power caps ??
Which capacitor cause problems in zobel network i read in one of your post??
Electronics is very new to me but i know how to use meter and soldering is good fun for me .
I would appreciate your help.
Love Rotel Sound and would like to preserve it.
Best of Regards .
I have both service manuals if needed.
 
Anyone ???
Basically the amp is running DIY Usher floorspeakers 2 midbass and 1 tweeter and is plays great when fairly loud but at low volume it sound dull. also sometimes it feels as if there was a blanket on speaker like there is no mid frequencies not always tough.

I would like to replace main filter caps 10000uf 63v with
MAL225658103E3 Vishay

22uf 63v and 220uf 63v with panasonic EEU-TA1J220BJ and EEU-TA1J221
for the signal path planning on using Elna silmic II and film capacitors vishay and wima. That is for power amp .
with the preamp i have no clue .
what other components i may think off ???

both of them are roughly 28 years old since there is all black gate caps i would want to preserve the character.
Please help.