If you want high-grade, super-clear sound, you must keep a purely digital connection, or at least use a TV with an actual line-out and balanced cabling, if you want to go analog.
Although it does sound like you maybe already own the TV, but then want to buy an Apple TV; so if that's the case the answer is very simple, yes that will work, of course assuming your TV has a headphone jack.
So in other words, I would suggest buying a different TV; make sure you buy a TV with some type of digital out. In this sense I think '@norcal Johny' is right-on here, with his answer above. Surely though if you haven't just already tried this out, you are planning a future purchase or a gift.
If you use the setup that you asked about, your audio is likely to get degraded in at least the following steps:
- Internet compression (if applicable) & wireless degredation
- Poor re-amping from the [likely cheap] headphone-amplifier inside the TV
- Noize from using unbalanced RCA cables
- Noize related-to that fact that your plugging a hot signal into a line-input, likely, on your amp.
DISCLAIMER: Your idea, may actually be the most common way people get audio out of an Apple TV. It is not suitable for so-called "audiophile" listening though, for sure, in my opinion even not for the average cinema fan, if you're really into nice, rich sound. As well, in my observations, the sound from Apple TV in general is somehow distorted at least slightly, to begin with, perhaps due to the wireless transmission.