I've been searching around and have not been able to allocate anyone around the west des moines area of Iowa that can do 3-6Mbps over fiber. We currently have one T1 and its roughly 450/mo -- which I thin is a bit high, although netINS has been pretty reliable in our area. I'm trying to upgrade and find the best deal possible. If anyone has any hints, please let me know.
Mediacom can do it over fiber. Depending on where your site is and how close they have fiber, it may be an OK deal. The circuit itself we have performs great and we havent had any issues. The sales process was pretty painful and they charge for ip addresses which i dont like, but in the end it works good. If you want a contact let me know.