Most sound cards these days have the (orange) connector for a 5.1 sound system; I have heard really good things about Auzentech's line of sound cards, great sound and the ability to upgrade the OPAMPS depending on your wants or needs.
" All of Auzentech's soundcards support swappable OPAMP sockets, allowing customers to upgrade to higher quality OPAMPs..."
http://www.auzentech.com/site/products/cards.php

http://www.newegg.com/Product/Product.aspx?Item=N82E16829156015 or another one that is a little more reasonable http://www.newegg.com/Product/Product.aspx?Item=29-156-012&SortField=0&SummaryType=0&Pagesize=10&PurchaseMark=&SelectedRating=-1&VideoOnlyMark=true&VendorMark=false&IsFeedbackTab=true&chkVideoOnlyMark=on&Keywords=(keywords)&Page=1#scrollFullInfo