Originally Posted by
Moisture
Try different stems and saddle positions instead
No. Just no.
Assuming your bike fit is dialed in, leave your stem and saddle alone. Regardless, there is nothing about these variables that would affect ride smoothness to any noticeable degree.
OP: for the riding you described, you will get much wider variation in ride smoothness with different tires. If you are currently running a stiffer, less compliant tire, you could try something like
this and get a significant improvement in ride quality.