Most hosts that offer 100TB are overselling. 100TB = at least 330Mbit which is not cheap no matter how much bandwidth you have.
With such bandwidth requirements you are limited basically to USA and certain parts of Europe. You won't find that kind of bandwidth in Asia or Russia, at least not that has good international performance.
What kind of budget do you have? I think once you've got bandwidth costs to think about, hardware will be a minor consideration.
You can consider Choopa/Constant (
http://choopa.com /
http://constant.com). They offer high bandwidth plans and have the capacity. They used to host fileserve.net and as I recall their speed was pretty stable. In case you don't know or don't remember, fileserve.net was huge and their bandwidth consumption was enormous.
Hardware wise, depending on what else your machines will be doing, serving files requires little in the way of resources (other than disk I/O and bandwidth) so high specs, I don't believe should need to be particularly high. Raid is definitly worth investing in given you DO NOT want to lose TBs worth of data due to hard drive fault.
You can also consider Constant's object cloud storage which is based on S3. You don't need to worry about managing the RAID and it is expandable to many many TBs. Cost is reasonable too at around $0.06 /GB.
If you think you will have duplicate files uploaded, you can save space by writing a script/program to compare files and where multiple copies exist you can just delete the multiples and create simlinks (or reference) instead. When paying per GB it can save you a ton!