Problem with ß character and lacking German supp ort

I have tried out aspell today, using German documents. I have found out
that the ß character is not rendered correctly here, locale being
en_US.utf8 and terminal being urxvt. Also there seem to be some flaws in
the German spell checking, as it does not mark "Das Große Auto ist
schön" as a mistake, although it is for "Große" must be spelled "große",
lowercase, for it is an adjective.
Are there any patches or alternative dictionaries for this?

Thanks in advance.