well i have a 1.5 and after 2 hours or so of audio recording/editing it gets hot, but i guess thats normal, for all the processing its doing, next buy will be a stand with fans, like the iBreeze from macmice. Also i dont think there's so much difference between 1.5 and 1.67, i think it will not be noticiable at least for me, but in heat problems, i think it will run like a 1.5 . I THINK, but lets wait and see