Are you planning on having any HA guests on your VM servers? If yes, you'd need shared storage (iSCSI,FC,NFS) between those VM servers, so that each server can access the guests vm.cfg and vdisks. Otherwise you will only have 4 independent VM servers, each hosting their own storage repository, rendering any HA setup impossible.
Afaik, the x3-2 offers 4 10GbE ports, doesn't it? You should be able to get decent storage performance from that from your 7320, depending on what gear the 7320 runs on.
Try looking at these Oracle Technical White Papers for some guidance on RAID and Storage configurations. As a general rule you will always get the best performance and protection from a RAID 10 (1+0) configuration. I know from my own experiences of running VM's on RIAD 5's, 6's, and 10's that I will only run VM's on Raid 10's. The RAID 5 and 6 are far too slow for Production VM's . If you do use Raid 5 and 6 for Test/Devl VM's be aware that you may have serious disk I/O latency issues.
Good luck, Russell
These are more recent documents that may help.
These are older documents that may help.