Hi Vivienne,
I have no idea why a perc card has been recommended, your board does support RAID and the controller is more than up to the task.
RAID is the best way for business setups as you will not technically lose and data, but there are alternative solutions.
The thing to bear in mind is that all drives have failure rates and when you add 2 in RAID that chance is doubled but the backup is there.
I am surprised that he has not recommended that you store the data online as it is then not using your resources as in the cost of drives.
There are alot of companies that offer the ability to manage your data over the web and they have all the means in place to offer you basically an outsourced server and with that you get the bonus's of data recovery/disaster recovery and low costs - if you prefer to keep the data 'inhouse' then use RAID (Mirrored)
hope this helps and please feel free to ask any more questions you have.