I saw the Dell U2412 in the low $300s the other day.
I have the U2410 version which has display port, HDMI, 2 dvi, VGA?, component? Composite?
An added bonus is that it will send the AppleTV HDMI audio out a stereo 1/8" analog jack to external speakers.
I really forget the exact connections but basically anything you could ever need.
I'm not a Dell fan but their mid/upper range LCD monitors are really good.
Plus they have, or at least mine has a 3 year warranty which is much better than apples.