I've had "stereo TV" ever since I bought my Beta HiFi about 30 years ago.
The HDTV I got in 2007 has analog audio outputs, so nothing really changed with that other than moving some wires around.
I don't think I'm interested in a full blown surround sound system, at least not yet. For starters, it's not obvious that there would be enough room to put all the speakers. I currently have two small speakers on the floor, because there really isn't any better place to put them.
I've noticed Soundbars seem to be popular lately. I've noticed this model in particular at Target, Best Buy and Newegg:
That would fit well, as the bar is "short" enough that I could put it on my TV stand in front of my TV, instead of on the floor or having to mount it somewhere.
How much of a difference do you think I would notice going from an old 2.0 system to a new 2.1? Most of what I watch is relatively old by today's standards. The median "filmed year" for my movies is about 1977. Watching movies, I sometimes have trouble following the dialog. I'm thinking that having small speakers on carpet might be muffling the sound somewhat.