S2600CP2 - Can't load ACHI drivers in Server 2012R2 for Samsung 840SSD

In a working Windows Server 2012R2 system on an S2600CP2 board, I have four non-RAID drives installed on the AHCI controller, and the SAS/SATA Capable Controller is disabled.   On that controller:

• 2 Samsung 840 Pro SSDs on the 6GB/s ports 0 and 1.
• a Samsung 840 Pro SSD on 3GB/s port 2. 
• a 2TB Western Digital WD2000FYYZ installed on 3GB/s port 3. 
• a DVD/CD drive is installed on port 5.

The "ACHI Capable SATA Controller" is set in the BIOS to be in [ACHI] mode.

Windows Server installation detected these drives and under the Driver Properties tab of Device Manager properties for the SSDs it lists:
Driver Provider: Microsoft

Driver Date: 6/21/2006

Driver Version: 6.3.9600.16384

Driver Signer: Microsoft.

I'd initially had VSS errors with Windows Server Backup on these SSDs and the 2TB WD drive  (backing up and external USB drive).  Microsoft support was able to correct this by setting paging files on each SSD and various other tweaks. 

A technician on SAMSUNGs support site said there were no special drivers for them - but noted that in the Device Manager they were listed as SCSI drives & that was not good.   I removed and redetected each device - and the 'SCSI' disappeared from the description, but the driver used was as noted above.

On Intel's download site for Windows Server 2012R2 and S2600CP2, I found

RSTe_and_AHCI_Drivers_GUI_CIM_CLI_3.8.0.1111_2013.09.26.zip  v3.8.1111  dated 10/4/2013. 

And it was stated: "Note: Package Version = 3.8.0.1111 adds support for Windows Server 2012 R2"

Splendid I thought - I will update the drivers.

I downloaded and unzipped the files, and in the Device Manager I selected a drive, right clicked, and picked "Update Driver Software"

No matter how I tried, the OS would not update the drivers for the 2TB or the SSDs.  When I selected the driver myself from those unzipped to:

G:\DOWNLOADS - INTEL\Intel RSTe_and_AHCI\RSTe_and_AHCI_Drivers_GUI_CIM_CLI_3.8.0.1111_2013.09.26\Drivers\x64_win8_server12\AHCI

this error was presented:

The folder you specified doesn't contain a compatible software driver for your device.  If the folder contains a driver, make sure its designed to work with Windows for x64-based systems.

1. Should I even attempt to update the drivers?
2. Why can't the drivers in this folder be installed on Windows Server 2012R2 when the documentation says they are supported for that OS?
3. I don't have a lot of experience at this - what am I doing wrong?

Thanks.