You know you can add an SD card if you run out of space right? It is definitely not worth $50 for 16gb more, when a 32 GB SD card can be bought for $20
Not much chance of running out of memory. I have downloaded over 200 apps n haven't even used 4gb. I do have a 16 gb card installed with about 750 pics n videos n haven't put a dent in the available space on it. Hope u are enjoying ur new phone.