Your DAC should be able to push the Stereomour into clipping. Is this something you experience with all your sources, or perhaps just more with your vinyl rig? If you are experiencing this with your digital rig, be sure all your level settings are all the way up if you're using the USB interface.
I would not mess with the 33K resistors. Adjusting that resistor will make the balance control quite a bit clumsier to use. The Morquiet does also have some insertion loss as well.
Generally speaking, we see these kinds of issues when folks have a 5mV cartridge and a Seduction/Reduction (especially when the phono preamp doesn't have the applicable C4S upgrade), but very rarely with a digital source.
-PB