I've owned the ESW9s and had the ESW10s for an extended audition. I preferred the 9s, but thought the 10s were technically better headphones. If I was only going to own 1 pair of headphones, and didn't want IEMs, I'd get the ESW10s. Otherwise, I prefer the ESW9s because they're more euphonic.
The nex5 is adaptable to use an awful lot of lenses, and there are more E-mount lenses in the pipeline. You should also be able to find NEX3s cheap, because of their being discontinued.