Best Ways to Secure My Fence Against Neighbor Dogs?

I'm dealing with a frustrating situation as a single homeowner. I've got two schnauzers, a 10lb and a 20lb, who are generally non-aggressive but reactive towards other dogs. This has created major issues in my backyard since my neighbors have large dogs that dig and attack the wood fences. My pups don't dig or attack but just bark back. The neighbor's dogs have broken through existing chicken wire and even dug under the fence, putting their heads into my yard and biting my dogs. I've tried various small barriers from Amazon, but these dogs are still managing to get to my pups. What can I do to effectively secure the perimeter of my fence? I'm considering options like fencing pickets, 4x4s, or landscaping with river rock. What's the most affordable yet effective solution here? My yard is quite large and I own a full southern stretch of the fence in the backyard.