ITunes download issues, should I invest in Apple TV?

We watch most of our favorite TV shows via iTunes.
We keep getting an error -50 on certain episodes. It’s really frustrating because we can download a whole season and episodes 2 and 6 will not download.
Apple says that it’s either a firewall, spam filter or connection problem but I think we have ruled all that out.
We are thinking of getting Apple TV thinking that it might be more compatible than our PC.
I have been looking at the Apple TV and don’t understand why eBay has them more expensive than the $99 straight from Apple. What’s the difference?
I am one of those people who know just enough to make a mess of things when it comes to technology.
Any advice?