Don't get me wrong but when I hear something like this, it often sounds to
me like someone is trying to upgrade a Ford Mondeo to be a Ferarri.
It won't happen unless you redesign the whole machine and then you can edit out
the B&O logo on the front too as it will end up very far from what B&O designed
and intended.
The Beomaster 3000-2 is a superb machine in its own right.
It was very high quality when launched but it was never built to be
an audiophile receiver.
A chain is never stronger than its weakest link and even if you can do a
lot by replacing old, dried out capacitors, that are not longer up to par,
there will still be many other factors acting upon the sound quality.
The choice of small signal transistors and basically the whole circuit
design will show its limits.
And you can start by eliminating the row of pushbuttons, they are nothing but trouble
when it comes to small signals.
Of course, it also depends on what you are striving for;
A modern sterile and linear or the original warmer and a bit colored sound.
In short, mount what you think sounds best for you and don't blindly trust
expensive components to be better than cheaper.
I've found "computer grade" capacitors very good for the output stages.
If you can find suitable sizes, you can fit 6800uF here to improve a bit on the damping factor
but no need for low-ESR types really since the output stage emitter resistors are the ones setting the limit.
Martin