I'd up your budget by a few hundred dollars and then you'll be able to buy a good quality bike.....$400 won't buy you much.

The Salsa Vaya is a nice bike and gets lots of praise for touring and commuting. It might be a bit too expensive at around $1500, but you could look on ebay. Also the Bianchi Volpe
is a good bike and can be had for a couple of hundred less and for under $1000 on ebay.