Fran,
If I were to name the "best bang for the buck" keyboard, I would name Casio's WK series. They offer a lot of keyboard (76 keys to be precise) for the money. It is fairly well built too. No, I do not work for Casio, but had one of the WK keyboards and had absolutely no complains about it. I moved to Tyros 2 which cost me exactly 10x what I paid for the WK-3000. Unfortunately, as amazing the Tyros 2 is, I am not sure if it is 10x better than the Casio.