When ZoE was a puppy, I bought pool noodles (those long foam poles used to float in swimming pools) and cut them to length with a serrated knife to fill the space under my sofas, so that she couldn't get under the furniture. 
 
It was a cheap & easy, and it also stopped balls & toys from rolling under the furniture too! 
Congratulations on the new puppy!  Love the name Piper 
