Hi, Apologiesfor delay. was busy and was not able to come back quickly.
Ok, For cisco servers you can try this image Cisco Custom ESXi 5.1.
These image will be custom built and tested to work with Cisco Servers. To make sure your Megaraid is loaded during re-install, Just make sure you have created the RAID 1 volume on the controller before you re-install the new ESXi image.
Hope this helps
AKU