Which is the best method for advertising a horse for sale nationally?

I have 2 andalusian horses with exceptional pedigrees I have advertised locally, but I have not had any responses. I am looking for other options and would appreciate any ideas! Maybe it is the slow economy, but I am not sure if I am not promoting them correctly. I do know since we are very small, our prices are much lower than the other local breeders, so it is not that we are overpriced.