I don't remember the last time I've used desktop speakers. Maybe 10 years ago? When I used to use actual speakers, I just hooked it up to my home receiver. My setup though is having the computer as the main entertainment center, I hook up my TV in dual monitors above my monitor and use it for video while I surf the web on the monitor, so I can use the receiver for the audio or the TV speakers or a set of headphones. Then I can just switch the inputs on the TV between computer, cable, and PS3 ( or as I call it, the expensive blu ray player ).
You can spend $400 on a console and $400 on a cheap PC, or you can spend $800 to build your own and have the best of both worlds.
Currently using Bose Companion 5, I have been using it for 2 years now. Previously using Altec Lansing VS4221 which I have used for 6 years or so since my university years. In addition, I have a pair of Thonet & Vander Kugel as a makeshift ipod/3DS 'dock' (well, not a dock at all)
I guess I upgrade because I am starting not to get satisfied with the sound. I used to be a basshead, but then, I took an arrow in the knee, i mean my ears get better and I want something more accurate and not boomy.
My next upgrade? Probably a DIY home theater with bookshelf speakers and external amp. $2500 perhaps? I don't know the price.