As of 1.9, haproxy can cache files as well. Well, 1.8 technically had caching, but more controls have been added around the cache in 1.9. The controls are not as fine grained as in NGinx, but it's fine for when you just need a small object caching layer.

Up until HAProxy 1.8, I used to have Haproxy -> NGinx caching layer -> Apache. I have since been able to remove all the NGinx servers. (For my use case, won't work for everyone)