But are no where near as good as my PC setup with imperfect files because I can correct for shortcomings in the source files.
You can't improve a digital file - if its junk it's junk. That long list of 1's and 0's is the same data whatever you run it through, while poor hardware can make it worse, you can never make it better - all you'll do is have a more accurate reproduction of the rubbish file you started with in the first place; it might do the hardware version of airbrushing to make it more acceptable, but it will still be junk. Alternatively, do a good quality DVD rip (of your own DVD's) or legal download and it'll look great through an AppleTV.
Additionally, I don't believe legal digital media should be 'imperfect'. *ahem*.
The PS3, XBox360, WD HD player, AppleTV, depending on the format your media is in are all better than trying to use a regular PC or mac from your sofa - if you can't commit to one because you want to play dozens of different formats, i'd suggest you get a grip of your media library before you start worrying about how to get it onto your TV!