2.1 setup

[Noufas]

I am thinking of moving to a 2.1 setup on my pc. I am after quality, volume if i need it.
What are my options? I was thinking of getting 2 speakers and a separate subwoofer. Will I need an amp for that?

 

[Noufas]

Like if i had up to 150 to spend? Or I shouldn't even try? I wouldn't want a massive amp (size wise)