I don't think you will hear more (louder) bass because the -3 dB point was already low.
Here's some info on (how to calculate) the -3 dB point or "cuttoff frequency":
https://en.wikipedia.org/wiki/High-pass_filter
With C = 47 nF and R = 470K the -3 dB point would be at 7,2 Hz.
With C = 330 nF and R = 470K the - 3dB point would be at 1 Hz.
I only just saw that your 330 nF coupling capacitors are rated for 160 V. That's too low. I see that you measured 171 V on the anode of the phase splitter, so that's already over 160 V (since the other end of the capacitor sits at ground potential, so at 0 V). But more alarming is that because you are using solid state rectification, the full B+ (which will be higher than normal at startup because there is no current draw yet) will be at the anode of the phase splitter in the period that the filaments are still warming up and the tubes are not conducting yet. Without current there will be no voltage drop over the anode resistor of the phase splitter. I advise you to choose capacitors rated for 400 V (or atleast 350 V) at those places.
The voltage rating of the capacitor at the input of the amplifier is less critical because under normal circumstances the voltage difference over this capacitor stays low (unless there's something wrong in the source connected to the amplifier). The value of 2.2 uF is unusually high (just calculate the -3dB point).