You can get a Naze32 pre soldered from some places.
But for a cheap and cheerful one you can't go wrong with a KK2.1.5. I even fly my 250 on default settings a lot of the time. The screen is really helpful too, although difficult to access in a small 250.
I will look out for pre-soldered one, although KK2.1.5 is a bit big for the 250's or just fit?