Speaker to be used with PC


I have a desktop PC which PC has what I believe are called 1/8" jacks in back for speaker connectivity. Since I'm starting to build an Itunes Library, I'm considering racheting up to a better speaker system. Worth it or waste? Suggestions, if worth it. Thanx.
lindisfarne
Powered speakers by Audioengines (model 2.0) work great with iTunes.

I also love the Blue Sky EXO connected to an iPod. You can get this at Guitar Center for $200.
Probably heresy on this forum, but I still use the powered Bose Roomates I got in the 80's to plug into my sony walkman for darkroom use. They connect via headphone jack of my G5, seen them go for as little as $50 on that "auction" site.
I am using Cambridge Megaworks 510D and they working fine since 2001, also get a RealTek High Definition audio integrated or external soundcard