@soosai steven since your speaker is grounded and amplifier is push pull for each polarity of signal, current is best supplied from each supply and ground to speaker to reduce impedance of source power, not between V+&V- . Understand that ESR of large caps may be big and consider you want 8ohm * C = 10*10ms for max out at 8* ripple. But ESR of caps can be big and needs careful selection of quality and additional shunt caps.
I will try to explain but it may be complicated.
Check cap dissipation factor D.F. or measure at 100Hz. If you have a woofer for 25 Hz then D.F. at 25Hz is 4 x worse. compute ESR and determine impedance ratio for woofer.
What dampening factor do you want for woofer? This makes bass clear or muddy from back EMF of cone mass.
Normally 50 is weak, 100 is ok , 1000 for the best PA's for best bass clarity punch like a great bass drum with dampening blanket and tuned port. Thus ESR must be << 8 Ohm/dampening ratio or 80 mOhm for df=100.
This Dissipation Factor for you, 100Hz (for me 120 Hz) ripple current heat ( Ipk ^2*ESR) with 10x speaker current at<10% duty cycle for 10% ripple voltage at full load. You may want better than this 10% to prevent 100Hz distortion.
The dampening factor is for bass step response (mechanical ringing from coil back EMF) are related both to ESR of cap and output impedance of power amp. The power supply ripple is in series with your PA and speaker and ripple reduction depends of feedback. Too much open loop gain, it will oscillate, too little and PSRR suffers. This is a design tradeoff. Even with this, a 20kHz snubber on output is essential.
It gets more complicated to explain but PA's are low voltage gain but very high current gain and supply ripple V sensitivity is poor due gain feedback and low open loop V gain , unlike preamp.
Thus impedance of cap must be very low 1/(2pifC) for lowest bass frequency 1 to 2% of speaker and ESR must be less. Since I know you can compute these, I'll let you decide. When I built my own amp in 1973 , I used 100k uF 63V, caps that were "computer rated " for mainframes with 100A ripple current rating. Then I added 470uF solid tantalum caps.
68kuF will sound better with two, one for each rail, but verify DF or ESR.
If you don't have a scope or spectrum analyzer , use Audacity to sample a scaled signal into PC aux input port, using sweep gen and Spectrum Analysis (free) or measure ESR of caps and compute your distortion and heat loss. Caps are thermally insulated, so the RMS current rating must have good margin for low T rise and long life . You can also use Simulators and add ESR to see the effect.