It will only make it worse. In Walnut the "adapter" of 100 Ohm is already built in It is possible to reduce the output resistance by soldering in parallel R7/R8 other resistors. 100 Ohms in parallel will give a total resistance of 50 Ohms. 10 in the parallel ~ 9 Ohms. This increases the volume, improves bass accuracy, but can increase background noise too.