Tracy - from Durand , MI
A firmer textured cake will hold up better under the weight of the fondant, which is why we recommend using pound cake. That said, if your cake will not be multi-tiered or have a lot of elaborate fondant decorations which would add weight, a cake from a boxed mix would work ok.
Another option is that most box mixes include a pound cake variation/recipe on the box, which isn’t quite as dense as pound cake from a mix or from scratch pound cake, and it tastes almost like cake from the mix!