I'm in the exact same boat! Tried the S3 and iPhone 5 and took a chance with the DNA and couldn't be happier. As far as the memory goes, I just took another posters advice and didn't add songs I wouldn't listen to anyway and still have plenty of memory left over.
With Google Music, all of my music is loaded into the clouds as soon as I rip it on my PC.
I can then choose a few albums that I want stored on my DNA to listen to, if I happen to be without wifi.
When I'm at the gym, they have free wifi, and that's the primary time I listen to music, so it's really a non-issue. Honestly, how many people need ALL of their music available on their phone?
When I get tired of those albums, I can have them removed from my internal storage, and new albums loaded on.
After two months, and having loaded just about ever app I want or need, enough music to satisfy my needs, and my photos in the clouds, I still have 4gb of available memory.
Really love the DNA! It has it's flaws, like all devices, but it more then makes up for them, for my needs!