I came across your 11 year old post and hopefully you are still on ancestry.com.
My great great great grandmother is Jettchen Speyer of Guxhagen who married Michael Plaut. I trace my Speyer ancestry back to Salomon Speyer, whose grandson Aron is the first one for him we have records that he was born in Guxhagen and also the family of Mendel Speyer. I don't think that I have any Speyers who came to America before the civil war and my family tree of Salomon Speyer has over 1300 of his descendants. My grandmother was born in Guxhagen and left Germany in 1939. I would love to compare notes with you.