I have a Sony MHC-RV8 (4.1) VACS. I need guidance to connect my computer with the MHC-RV8 and use the 4.1 Channel audio.

[Aravind Raja]

I have a Sony MHC-RV8 (4.1) VACS. I need guidance to connect my computer with the MHC-RV8 and use the 4.1 Channel audio.

I currently have connected it on MD(Video) mode and also tried with Game mode and connected with computer using 3.5mm to 2RCA . In my computer it shows as 2.0 but all the 5 output speaks(4 speakers and 1 subwoofer) are working but I do not see audio separation, Please assist what ways are available to use my it as true 4.1 form Computer input to MHC-RV8 output.
Is there any cheap external device that I can use if there is no default options to use 4.1 channel audio?
I don't know anything about audio
My friend said I should replace the Unit with a different amplifier and use the speakers in 4.1 or 5.1(by adding any other speaker to them for Center channel) and connect it with my computer and use it?
What amplifier should I buy or is there any other cheaper alternative?

*It says 7000W PMPO I think the RMS is around 1000W Attached screenshot of the speaker specs