not sure what .SEA is
.RAR is the first file in a Rar Archive set, .R00 is the 2nd, .R01 is the 3rd, .R02 is the 4th, and so on.
.DIZ isn't an archive...file_id.diz or whatever is what you are looking at right? It's some kind of checksum or something I think...not sure what it is, I used to see them all the times in my old Warez days I always just ignored them.