I used to try to eq first because i know even my mixer's eq's sound better than the plug ins i have. And it does. But, you really don't know where you need it until you have everything else. For example, you might want to fatten up a thin sample. Then you realize a fat bassline will take up those frequencies so you eq out what you did. Or you might just have conflicting things. So i wait until i'm totally done and ready to mix. There are exceptions though. If something has a really nice bassline and i know i'm going to filter it (and low cut the main melody), i'll eq. Drum loops, i'll eq. But in general, i find it better to wait until i mix. It sort of like the "measure twice, cut once" deal. To re-eq is basically de-eq a sample which is pointless and can lead to bad results, or atleast be time consuming.