Well if ya want tons ya could go SCSI aswell, but at the end of the day ya gonna run out of room in ya case aswell, unless ya get some sort of external housing.
you can have one extra ide hhd on the 1st cable / one extra ide on the cd-rom cable / and one external hhd using the usb ports, depending apon how many usb ports are available. and then think of how many partitions each drive will have.