The RAID configuration you current have is based on the SAS-midplane board (Active Midplane). This setup provides a direct connection from the RAID controller to the backplane. This is why you might notice that there are no cables from the RAID controller (midplane) to the backplane.
In order to use your Adaptec* card, we need to remove the current midplane and install a passive midplane (see image) which will allow you to connect your RAID controller to the backplane.
Although the RAID configuration is stored in the drives, it is uncertain if your replacement RAID controller would import the configuration of the drives.
Feel free to approach Intel Customer Support for proper follow up on this process.
The ordering code for the passive midplane is FALPASMP. You may want to contact Intel® resellers to find out if the still have the part available.
In the past, customers have been able to locate the item on online retailers such as Amazon.com, eBay, etc.