Hi all!
I am looking to replace my Klipsch ProMedia speakers and sub that I use on my PC for something better. I am probably going to want passive speakers and a sub. My first question - how do I connect passive speakers to the computer? Can I use a soundcard(not really sure what these are for lol)? If not, what would be a good amp?

Budget is around 500-600.

I am used to great audio as I have some BT-1990 open backs with xDuoo TA-30 so I want something good, but I rather not spend as much on the speakers as I did the headphones.

Style wise - I am trying to go for a mid century desk setup, so something with that kind of stylization would be great. So all in all, I am looking for a pair of smaller(that would sit on the desk) speakers, with a sub. Passive preferred. TIA!