Advice Needed On Recapping Power Amp

I agree that it is very unlikely that you actually need caps replaced at this point, but if you are after a modification that would help. I can see that. I have replaced power supply caps on a few amps with very good results.  
4 things that you need to seek is lowest ESR possible and highest capacitance that will physically fit along with voltage of at least that of the rails of the amp and high enough temperature rating.  
Most supply caps are 85 degree parts.  That should be absolutely fine... If you had a pure class A amplifier, then maybe move up to 105 degree parts,  but 85 degree typically sound great and work well. 
If you have say a typical 10,000 mfd supply cap at 85 degrees and 63volt part.  Look for the highest value capacitance that will fit that meet that 85 degrees and 63 volts(or higher)  
I just replaced the power supply caps in my old Sumo Nine.  It had 85 degree 10,000 mfd 63 volt parts.  Because it is pure class A, I moved to 105 degree parts and found 22,000 mfd, 80volt parts that would fit that ended up having very much lower esr than even the Panasonic caps that I put in there back in the late 80's.  

For any Electrolytics on the circuit board.  Those circuits often would have very much different results change the values,  so other that raising the voltage try to keep the exact values of the caps that you are replacing and all will be fine. 
But again,  none of this should be a NEED for your amplifier. 

Going from a stock value of 10,000uF PS filters to 22,000uF is a very good way to destroy your transformer and rectifiers unless you're pretty sure the current limiting of the power supply will adequately choke in-rush current. If very low ESR is your goal, bypassing with very low ESR caps is more effective. 

Hi   @kosst_amojan    ....  Well, I guess that really depends quite a bit about your transformer first. My knowledge is limited about "Inrush" current.  
To those reading these comments.. In-rush current is the current flow into a product when you flip on the power switch.  It can be quite large.  That is why on some of these old beast of an amplifier, you see the lights dim when you fire them up. 
I am not a indepth as some others, but as I understand it,  the larger the transformer, especially in toroid types are more susceptible in passing current. When caps are idle,  they look like a dead short,  So the VERY IMPORTANT part here is.... The Low esr along with natural wire resistance is the only filter for this current (unless there is a soft start circuit)... I have done this to maybe 5 or 6 amplifiers.  NEVER had an issue.  Each time, the amp sounded better, but I yield to opinions of those in the know. 

recap not needed. don't waste time.

Going to higher capacitance means also higher inductance hence slower response to rapid current demand.   It will also reduce ripple and that might not be a good thing, since very low ripple, especially when combined with low ESR means very high and very narrow current spikes charging capacitors and that might couple to any inductance in the rest of the circuit.  I would agree with  kosst_amojan and would not try on my own to redesign an amp.  In some cases it might work in other it could make it worse (or damage rectifier).

Bypassing slow large inductive caps with fast low ESR cap might be not the best idea, since it creates parallel resonance circuit that might ring.  Better option would be to get low inductance electrolytic caps (like slit foil type), but they are expensive.  Better yet is not to "redesign" something that works just fine.  There is also an issue of reselling such "improved" amp.

15 year old capacitors, unless they are in very warm place, should be good for another decade.