If you really want to buy anything in NEX series then get NEX 5N which is getting very nice reviews all over the internet.
Earlier models in NEX series were OK but were behind their competitors including NEX-3K/B.
Following is to be kept in mind for Sony NEX series before u decide:
- Very limited number of lenses available and these are expensive as compared to their competitors in Canon and Nikon range
- No flash
- No hotshoe for external flash instead u will have to buy a separate flash adapter+flash
- No external mic jack
- No viewfinder but again u can use one with the help of an adapter and both viewfinder+adapter have to be purchased separately.
I was never a fan of viewfinder before getting my DSLR and always used LCD but it is a big help in keeping your hand steady and making a better composition and now i only use viewfinder
I have personally compared the shots of Canon 550D, Nikon D5100 and Sony NEX-5N on imaging-resource and Sony has better results than the other two in low light.