Surround sound from 2.0 desktop speakers

Currently have a surround sound set up on the computer, speakers plugged into the motherboard's sound outputs. I dont care for surround sound , my rear speakers aren't even plugged in, but I do like surround sound for gaming. So for that reason I leave the sound output options on the computer in 5.1 and when using my headphones plugged into the microphone out on my centre speaker (logitech setup) I still get my surround.

But I am ditching the surround speakers in favour of the Creative T20 or T40 2.0 speakers.

I still want though surround sound from my headphones when plugged in.

What are my options to achieve this.