After I bought a Sony 200W sub on Black Friday I noticed that the sub has its own plug, and its a powered sub.  Meaning that it doesn't have to draw power from the receiver.  I also noticed that it has extra audio connections, and I'm pretty sure you can connect speakers directly to the sub.  So I was thinking that with a powered sub and a pair of bookshelf speakers you could possibly make one hell of a 2.1 setup.  The only problem that I found was when I set my bookshelf speakers next to my monitor it didn't look so good.  I'm actually going to stick with the speakers that I have for now, but I thought that it might make an interesting discussion.  The price isn't that bad either, you could do it for the same price as several of the high end 2.1 speakers on the market, $150 - $200, and I bet they would sound better, and be a lot louder.

here are the speakers and sub that I was thinking might work.

 Sony SA-W2500 100-Watt Performance Line Subwoofer

Sony Bookshelf Speakers 

Sony Bookshelf Speakers with mid