"I guess 4 GIG is the max...right?"
It depends upon the version of the OS and the file system you intend to use. 4 gigs is a lot space for relatively compact Amiga files, especially if you keep your Mp3s and video files on CDs. Caution: the temporary files generated by browsers tends to corrupt and shorten the life of a hard drive.
I run with two 4 Gig HDs, one is a back-up of the other (they are partitioned the same).