Use a stereo with an auxiliary input and drive the speakers from the stereo. The small amp in the computer wont like those speakers and you could kill soundcard as well as it might not be very loud until the secret smoke is let out then no sound. A headset is about all you can drive directly from a PC anymore without an amplifier to drive the speakers.
Just need an amp or stereo with aux input and connect line out to aux input. Then make sure volume is low and test. Raise volume to level you like from their or have Windows chime blow the windows out of home if set to max volume on boot..
I have a 80 watt Roland Amp for my electric guitar that has an aux input and that is LOUD. I made the mistake of forgetting my volume on my PC was set to 100 for headset and wow that woke me up fast when the computer made a sound. My amp takes the aux input and sends it out at 100% so the PC has to be used to regulate the volume. The volume knob on the amp only controls the guitar that its driving the sound from. It has a direct input to 100% of 80 watts of speaker. Just about jumped out of my skin when so unexpected!