We talk about this quite a lot in the following blog post:
http://www.multichain.com/blog/2016/07/announcing-the-new-multichain-wallet/
In general, you can treat 100 transactions per second as a safe rate under most normal circumstances, including complex multi-asset transactions and writing to data streams, all on a low-end commodity cloud instance. Keep your transactions very simple, and use high end hardware, and you can get close to 1000 tx/sec.