We use Amanda Enterprise to back up directly to S3 (no intermediate staging).

This takes our standard SQL backups and all the non-DB files that need backup and puts them all on to S3.

We were one of the early customers needing to back up large volumes to S3 in a Windows environment, and it took a while to get the throughput we needed, but once that was passed Amanda has been stable and reliable (and MUCH cheaper than the usual suspects for enterprise backup). It should easily cope with the data volumes you mention, we have more than that.

Be careful about using Glacier. The cost algorithm for data retrieval IMHO does not match the Amazon promise of 'pay for what you use', and can give very high costs. If you need to restore a 2TB file and ask for it in 50GB chunks over 2 days you can get the restore done for free, but if you ask for the whole 2TB in one go it can cost thousands. We are waiting for a more friendly restore cost algorithm before using Glacier again.