$100 for an extra 32GB? That's a pretty steep price for storage. Consider this:
Amazon.com: Samsung Electronics 64GB Pro microSDXC Extreme Speed (UHS-1) Class 10 Memory Card (MB-MGCGB/AM): Computers & Accessories
There's 64GB of extra storage, Class 10, Professional grade, for less than $1/GB shipped. And it will be just about as real-time fast as built-in storage... with the added benefit of removability.
Go ahead and buy the 64GB version if you want to, but a 32GB phone with the above 64GB card will do just fine for me