Craig,
I think you misunderstand. It is just the lettering. The extra sata card is not going to be booted from. The bios only sets the boot order, not which drive letter linux is going to assign it. it is the drive letters that just annoy me and was hoping for an easy changeable fix. I was surprised anaconda installer had no option to change them.
It is like installing windows on your f drive and having c and d as storage drives...just rubs ya wrong.
It boots fine from sdc with or without card in it...it is centos labeling based on how it looks at the hardware. Apparently an add on sata card comes first in the order linux analyzes the system.