Gulp!! my experience with anything graphic is more GPU and less CPU. However having said that in your case I'd probably choose integrated over discrete graphics simply as you have eluded to, the potential for over heating, especially in lengthy rendering jobs.
IMO don't disregard outright the integrated solutions offered by AMD. You will find they are a bit less pricey, but also full featured. AMD systems are strong in multi-tasking environments so have quite a lot to recommend them.
My niece, who is a extreme video/photo editor, every bit a professional, went from Core 2 + nvidia (8600) discrete to AMD Turion dual core = 4000 series Radeon and loved it to the point she is now pricing out a new Bulldozer system. She found that the pricey Intel system would consistently crash during sustained multiple sessions, with the GPU burning out twice before ASUS replaced it with the lower power 8400 with considerable loss of grunt.