Yes, that does mean that a hi-fi speaker with a 12 inch bass driver will be a lot louder for the same input than a PC speaker with a three inch driver. With a reasonably efficient speaker, a weedy little two watt sound card amplifier is more than adequate for room-filling sound. As a matter of fact, most hi-fi listening is done at power levels well below five watts per channel. The other important speaker statistic is frequency response, which is another thing about which cheap speaker specifications usually lie. Most adults can't hear above 14kHz, but that's not where the lies are.
Cheap speakers tell fibs about their bass response.
No matter what a cheap three inch driver's specifications say it does, it has no useful response below 120Hz, and probably bog-all below 200Hz. Yes, it will make a noise if fed a 50Hz tone. But it's so inefficient at that low frequency that it'll barely be audible, even at full power. Or just use bigger speakers. If your sound card has an amplifier, all you'll need is a cable to connect the sound card to the speakers.