Ooh, Ps.

Ram can be confusing to choose between
you will see stuff like ECC and Non-ECC
and numbers all over the place

the ECC stands for Error-correcting code
personal opinion, but you don't need ECC memory
others may say different
but I'd recommend non-ecc ram

numbers:
basically, bigger numbers = faster
these days, the numbers tend to mean Mega-bits per second
so 6400 would be 6400 Mb/s = 6.4 Gb/s

hope this all helps