1) The Graphics Card is blowing air across all the critical card components so being near the heatsink won't matter.
2) Note that the "GPU" is just the main chip on the Graphics card. If you mean graphics card, just say that not "GPU".
3) *Just FYI, but the GTX980 only performs an average of 14% better than the GTX970 but it's roughly 67% more expensive. It does beat the GTX970 by up to 19% in a few games.
Overclocking is also likely to change the above as I'd imagine a card like the Asus Strix GTX970 might overclock a bit higher than the GTX980 (at least in an acceptable NOISE limit.)
Personally, I'd get the Asus Strix GTX970:
http://www.techpowerup.com/reviews/ASUS/GTX_970_STRIX_OC/25.html