umm..to my exp with cyma is good.
only thing is if you are looking for a metal body, CYMA might not be the one to go for...their metal is crap..not sure about that M4, but the MP5 from CYMA has really crap metal. I used a magnet and it barely sticks..the mp5 was really heavy too..same weight as my KA M4 with all the metal accessories attached...(metal RIS, peq + lipo, full metal acog style scope)
But for the functionally I think CYMA is just fine. Although I prefer KA with that amount of money...or just add another 150ish to get a VFC...