Speaker issue

So I recently purchased some new 5.1 speakers for my media PC as my old ones broke.


But, there is an issue only two of the speakers are working.
The ones which are plugged into the green audio jack, I assume that it is my motherboard not being able to properly output the sound.

Link to speakers: http://www.ebay.co.uk/itm/like/Creat..._qi=RTM2063723

Link to motherboard they're being used with: https://www.amazon.co.uk/ASUS-760G-U...2B+motherboard

Yes, I know the motherboard is a little shitty and cheap but the PC is only used for movies and music so I don't care about it being upgraded any time soon...

So, I am debating whether to purchase a sound card but am afraid that this is not the issue and I will have just wasted my money.
Let me know possible fixes/solutions down below.

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