Ah right, forgot about the tuner, but it's not like you couldn't add one. I added one I had laying around to my compaq(which actually was pulled from an HP
)
The Sempron is just the cheaper processor from AMD. It's still a strong performer. I got one in my laptop, nice processor. I'd take it any day over Intel's Celeron!
As for those 2 machines you posted, I'm not a huge fan of either of those brands. However, if I had to pick one, I'd go with the emachines due to the RAM and slightly faster CPU.
And yes, if you capture something you can burn it to a DVD.