Sql 2014 express upgrade on desktop machine

Hello dear people,

I hope I am writing my question in the proper forum. Sorry in case I'm wrong.

I installed a desktop computer for a client of mine that uses an accounting software that uses SQL database.

The company installed SQL Express 2014 and now the database got over 8GB and it's time to move on. The server serves 11 workstations in an office environment.

The specs of the computer that acts as a server :

Intel Core I7 2600 CPU

Intel H67BL Motherboard

8GB DDR3 1600

180GB Intel pro 1500 SSD drive

2X2TB WD Raid in raid 1 mode

Windows 7 Pro X64 English

I would be happy to know if it seems reasonable to upgrade the SQL Express 2014 to SQL Server standard 2014 4 Core CPU + 25 CAL on the current system, So It can work with a larger database ?

My client is on a budget, And I've considered buying and installing him that version I've found on ebay :


I would really appreciate your guidance, So not to throw money away on something that might be incompatible for my client's needs.

P.S. Also thought to upgrade his computer to 16GB memory.

Thank you !