In its day the ATV2 was "The Device" to have to run XBMC (and are now way too expensive to buy second hand). Things have come a long way since then with many many different devices being available, which can handle streams (especially HD) better than the ATV2.
OUYA, Raspberry Pi are both options and will both play full 1080p HD with no problems whatsoever.
My ATV2 is great for streaming from my computer and watching Netflix, but Star Streams only works if I run SD streams. Which is strange, because the HD streams are not even close to being real HD imo. It used to be so much better.