Trying to set up 1st time sound set up

After the laptop which was my first computer died last month, I finally got a new 2nd hand computer and am puzzling through what to do about sound. Am starting from a point of not having anything to play through beyond having AC97 Sound Card on a HP DC7600 CMT computer
so am wondering what the best route to decent sound set up would be on a budget.

Would like to use computer as the sound source for my front room.
Just thinking that getting hold of a 5.1 surround system would be good.
Since I as yet have no speakers wondering what best solution on a limited budget would be. Not knowing capabilities of AC97 Sound Card do I need to upgrade to 5.1 card of some type? Am seeing several on ebay for seriously cheap and wondering if you get what you pay for.

Just thinking that if I do whatever now I can skip an intermediate stage of getting the wrong type of speakers for longterm goal. Or if I should get a cheap 2.1 set with subwoofer then save for something better.

So wondering if anybody has advice on options