Mutli-use speakers? Amplified speakers?

[dclee012012]

I just blew out the bass in my old generic 80 watt speaker. Finally going to get a new set. Here's the thing..

I just need 2 speakers (plus or minus a sub). And I want to use the same speakers for an acoustic guitar, and occasionally a keyboard. Any recommendations?

Also, when I play a guitar through the speaker, should I plug in directly to the speaker? Or into the sound card's line in?