No need to get another speaker. You can get a cable with 1/4 jack at both ends. 1 end connect the the green hole from the DELL monitor and the other to your soundcard (sound-in) hole. Thus your XBOX360 will output sound via your PC speakers just like mine (A PS3 though but it should work the same). Your PC has to be on in order to have sound output. Another option is get an AEGO M, it can support sound in via 1/4 jack

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