Server Configuration Reqired

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I'm Developing a desktop application using SQL SERVER 2008 R2 and C#.net 4.5 .The Application contains Various modules like Accounting,HR,Production ,Sales, Inventory etc. Database has more than 200 tables and expecting 10000 rows per month in at least 25 tables in DB . It also stores Image which has expected size of 10 GB per month. I'm Using SQL Filestream to do so.The Application will have 15-20 users concorrently. So what will be the minimum hardware requirement that I need to work my application smoothly .