If it were up to me, I would get the FEC filters also. There are so many filters in that package that are unique and powerful that it should justify the purchase. And where there is some overlap, there is also a lot of difference. To illustrate this take the Snow filter for example. In the BCC Snow filter, which come free with RED, you can generate snow flakes that can accumulate on the surface of an object, such as a title or an alpha map, and the FEC version does not have that function. However, the FEC version includes a perspective feature and motion blur that makes the snowfall appear quite realistic. I would suggest downloading the FEC trial filters and seeing if they make sense for you and your workflow.