The hardware structure is different so I don't think you can hack N5200 to support iSCSI.
as far as I understood some discussions in the firmware forum, just putting the 2.00.00.11 beta firmware or so onto the plain 5200 you get working iscsi. could be wrong though, didn't read too closely since it didn't interest me.
Gideon, you're right, with a beta firmware (should be the 2.00.01), iSCSI was fully operational on N5200 nonPRO.
I think the two reasons, why it should not "work" on the old model is: - Marketing facts: Who should buy the PRO if the normal version does the same work? - Performance facts: Multiple Raids and iSCSI are more CPU-intense and maybe the data throughput is a little poor with the 600MHz Celeron... but worth a test! :-)