Which speaker set should I use for my computer?

I currently have these speakers hooded up to my computer a href="http://reviews.cnet.com/pc-speakers/logitech-z4/4505-3179_7-31516456.html" rel="nofollow"http://reviews.cnet.com/pc-speakers/logi…/a . Is it worth upgrading to a href="http://www.bestbuy.com/site/Logitech+-+Z523+2.1-Channel+Speaker+System+(3-Piece)/9472652.p?id=1218111188355&skuId=9472652" rel="nofollow"http://www.bestbuy.com/site/Logitech+-+Z…/a or a href="http://www.bestbuy.com/site/Creative+-+GigaWorks+T20+Series+II+2.0+Multimedia+Speakers+(2-Piece)+-+Black/9238407.p?id=1218065495350&skuId=9238407" rel="nofollow"http://www.bestbuy.com/site/Creative+-+G…/a ? If so, which set is better?