Consulting the Adaptec documentation (nicely provided on the accompanying CD-ROM), it states it supports RHEL6 and to not add the "kernel dd" boot option for RHEL6 but to boot the DVD normally. Obedient as we are, we follow the directions. 

Here we go:

- boot the DVD until the graphical installer

- go to the console

- mount the driver floppy-disk (ehhr,  yeah right. Hello! 1990 called, they wants their floppy-disk back...)

- so mount the floppy .img file from USB stick (hail to: mount -o loop)

Sorry, no such luck. No storage devices.

Luckily, Google turned up with an answer.

http://cz-boot1.atlex.ru/adaptec/ has a working dd image and instructions for use.

Additionally, the crucial.com.au blog features a similar article at:

Both sources put a file in /etc/depmod.d to keep the driver working after 'yum update' (newer kernel versions)

However, I ran a full yum update (on Feb 22nd 2013) and rebooted without any problem without the depmod file.

Since I'm not planning to update the kernel package in the near future, I'll just leave it as-is. Working.

Now, continue with installing the OS.

When up and running (and optionally, updated) install the Adaptec Storage Manager:

- download the proper file from the following uri into /root/adaptec :

    http://www.adaptec.com/en-us/downloads/storage_manager/sm/productid=sas-6405&dn=adaptec+raid+6405.html

- unpack the file (e.g: tar zxvf msm_linux_x64_v1_00_20206.tgz)

- run the installer (e.g: ./manager/Storman-1.00.x86_64.bin)

To see your array configuration: /usr/StorMan/arcconf GETCONFIG 1

To check your array status: /usr/StorMan/arcconf GETSTATUS 1

p.s.  if you're only using the arcconf command line functions, you might want to disable the three storage manager services. They tend to eat up quite a large amount of memory! (on a pure-hypervisor host, that is not what we want). Use chkconfig to turn off: stor_agent, stor_cimserver and stor_tomcat.

Cheers m8s!