I recently bought a ravx stem for my GF x-caliber. It is a carbon wrapped stem called the Herculite. It seems really nice, but I have to admit that I took a chance getting it. I really know nothing about this company or its products. There is a local online store selling a lot of their stuff. He had some one piece carbon handlebars/stems that looked really cool.
http://www.ravx.com/2010_product_pages/product_categories/product_overview.html
http://www.ravx.com/2010_product_pages/product_categories/product_overview.html