Home-made Quadraphonic audio is so cheap to setup instead of a 5.1 system.

WARNING THIS CONTAINS a biased HISTORY and added drama.

Since using C=AMIGAs (they have RCA phono sockets) I have always plugged the audio into a proper stereo amp.
Oh my word, how we did laugh at PC owners in the 90’s when they discovered what they called “Multimedia”.
Finally adding a CD-ROM, bypassing the buzzer with a sound card, and adding 2 tiny little passive (un-powered) pointless speakers, and they were ready to rock…quietly.
Speakers that weren’t selling, originally intended for the personal-stereo market, now finally found a home standing/squatting proudly next to thousands of 14″ monitors all around the globe.
For the next few years while Amiga owners were switching their amp to AUX/Line In, and turning up the mayhem (Barbarian was so frakkin’ awesome!), while PC owners were fiddling with Windows volume sliders, giving-up, and leaving it all maxed-out (just like modern-day laptop owners).

Then doom happened for the Amiga, as quite literally DooM happened on the PC.
Now PC users expected to be blasted and pounded by the sounds of the 3D environment. This was the first major “killer-app” for the x86 platform. A single reason to buy something you never wanted before.
i.d. software refused to port or allow a conversion. Stating that it was beyond the capabilities of the standard Amiga hardware and graphics, and not enough owned a “big-box” Amiga, so they couldn’t see it as an investment. (Interesting as DooM started as a P.D. demo )
….
Story continues elsewhere…
(I seriously got choked-up writing that. Whew!)

…aaand back in the room.

CHEAP QUAD SOUND
Check-list
1) Most modern PC’s have at least AC’97 (6 channel) compatible sound chips, and at least two 3.5mm jack sockets (ironically Vista/7 users may have difficulty).
CPU-Z or System Information X will tell you exactly what chip you have, and who made it.

2) You need to have the full drivers. The “lite” ones shipped with windows will not do Use the full original drivers from the chip-maker. If you cannot find them, try the drivers from Realtek.
Vista/7+ users – Unfortunately Micro$oft don’t want anything to ruin the look of Aero, so some drivers do not install the manufactures own GUI. This can be a pain if windows will not let you over-ride the socket usage. If you change windows own speaker settings to “quad” it should swap one of your inputs into a second (rear) output (but you may have to guess if you have more than 2).

BEFORE updating the driver, this is a good time to also make sure your Motherboard chipset drivers are also up-to-date.
When you open the GUI/control panel for your sound card, you should easily find the options for controlling your sockets. If not, plan-B is to try windows own settings.

Methods
a) If you can, the best and cheapest way, and you just buy 2 audio leads
One lead should be a 3.5mm stereo jack-plug to (usually) twin-phono/RCA plugs or another 3.5mm jack. This goes from line-out to your amp/HiFi.
The second lead is a headphone extension cable. Plug this into your new rear-out on the PC, and you can find somewhere at the other side of the room for your PC speakers to plug back into a power-point, and then route the extension lead to the jack-plug (under a rug is good).
b) Next best, is to buy a second set of stereo PC speakers (at least as good as what you already have), and a headphone extension cable. Use whichever pair are best for the front, and plug the other in the end of the extension.
c) The total cheap-skate and weird to use method !
Plug a set of cheap mini in-ear, earphones into the PC’s rear-out, and adjust the rear volume so you can hear your front speakers clear as your earphones.

*Note the last method can scare the crap out of you with a surround-sound film