Zotac seem to have two versions of the regular GTX 970; one with a reference cooler and one with a twin-fan design. If you're looking at the twin-fan design, then no, the AMP! edition isn't worth the extra cash. If you're looking at the reference cooler, then yes, go for the AMP! edition.
The reason being is that reference coolers are terrible; they're loud and run hot, and the extra cash for better cooling is definitely worth it.