I have not heard of Tubus but that doesn't mean that they are not very good. Rivendell sells Nitto chrome-moly racks that look pretty bomb proof (and should be for almost $200):
http://www.rivbike.com/product-p/r4.htm. For about half the price, you can pick up Jandd's expedition rack:
http://www.jandd.com/detail.asp?PRODUCT_ID=FREXP. I'm a Jandd fanboy. I've used their gear extensively (and not just for bike riding). Jandd gear is exceptionally well made and it really holds up well over time.