I'm not sure you've thought through your list of requirements versus the capabilities of the AppleTV w/ ATFlash.
You say you don't need to stream from NAS, but you also want to watch movies. Even the largest AppleTV hard drive would fill up quickly. I have about 20 movies and a few seasons of TV shows and I'm over 200GB. Far more than the internal capacity of the AppleTV.
If you think you'll just transfer movies when you want to watch them, remember that it takes longer to transfer a movie than to watch it. This method doesn't work well.
I also can't recall there being an IP radio engine, though I could be wrong.
I'm personally of the opinion that the Mac Mini makes the best STB and can be had for only a little more than the AppleTV and Tvix.
There is scarcely anything in this world that some man cannot make a little worse and sell a little more cheaply. The person who buys on price alone is this man's lawful prey. - John Ruskin