Above is a push pull Amplifier. As we all know the 8 ohm speaker is not receiving enough juice from the supply rails, in fact its only getting around 16 watts of power, how can we double that amount to make it like 40 watts. It appears that varying the resistors value has no effect. How can we make the speaker receive more current (we can make it absorb more current by lowering the speaker's impedance but let's say the impedance is fixed at 8 ohms).
If there is a linguistic or cognitive challenge, then no comments. Otherwise, the Bridge-Tied-Load configuration remains one of the potential solutions to the issue. Also, it will certainly be simpler to implement than a boost circuit, given the circumstances.
As we all know the 8 ohm speaker is not receiving enough juice from the supply rails, in fact its only getting around 16 watts of power,
Of course it's only getting about 16W. To deliver 40W average power (with an undistorted sine wave) to the 8 ohm load, you must have almost 18VAC at the output of your amplifier. That's a little over 25Vpk or a little under 51Vpp. You can't do that with a 40V Vcc.
Since you loose some voltage across the base-emitter junctions and you'll want some headroom , the Vcc should be, say, 55V instead of 40.
And, of course, since the voltage gain is less than 1, your source voltage will need to be larger than 25Vpk.
Finally, your power supply must be capable of supplying the peak current and of sustaining the average power, the calculation of which I'll leave as an exercise for the OP.
Everyone has overlooked that you are losing half of your "punch" in the series output capacitor. 1000 uF is 8 ohms at 20Hz which is where speakers can be seen to punch. Of course juice is a punch so I am not sure what band that belongs to. Maybe rock N roll but more "real" fruity sounding than "punch" ;)
(levity helps when questions get monotonic or repeat themselves.)