You might want to check to make sure that board will support 4 strips of memory. Most motherboards will on support two strips if the memory is double sided (which most 256 chips are). In which case you would have to get two strips of 512 to keep the same amount.
As for the ECC, it really depends on what you are using it for. It it is going to be a server then yes. ECC is error correcting and involves some pretty complicated formulas. If it is going to just be your home PC then you probably wouldn't benefit any from it. Plus the ECC is just a little bit slower than non-ECC.