Your 160GB will have nothing to do with the 2x500GB.
Simply mount the 1TB array (2x500GB) at /home once its created.
I use linux software raid and its fantastic...
You can destroy, create and repair arrays without rebooting...
Also one great feature is that you can mix raid type.
For example, with 2x500GB (each drive in 2x250GB partition) you could :
2x250GB in raid 1 (250GB usable)
2x250GB in raid 0 (500GB usable)
If you just need the speed but not 1TB you could do that and do backups on the raid1 array.
, further down it explains how to create arrays with mdadm