I like your plan but i ordered a reaplcment cable as it was fairly inexpensive from amazon and can test it today once it arrives. If it still gives errors im gonna order a new HBA to replace it.
Let us know how it works out.
Update: Error has still not reoccurred since i swapped the boot mirror to be on that cable off the HDA. I have a replacement cable here ready to install but going to leave it another week before i change anything to see if it is all resolved.
Sometimes it is best to leave well enough alone 
Exactly why ive not changed it yet since errors stopped lol.
Just an update. replaced the cable, and that was ok for a while, but last week started getting errors on random drives again. I swapped out the HBA card a couple of days ago with a replacement and so far so good. Ran 3 scrubs since the new HBA went in and other than the first one wich fixed a couple of leftover checksum errors, no errors have shown up. Hopefully that has sorted it.
I guess the next step will be to replace the PSU if the errors recur.
Fingers crossed this has sorted it, though.
–Steve
Has @winnielinnie visited this post yet to recommend the needful memtest? Trolling aside, I swear he has a collection of a > dozen posts where that did fix/identify the issue.
Turns out it was bad Ram. Has now been replaced.
That would be very good if you never see that problem again.
How did you determine it was bad RAM causing the issue? Just curious and it could be a learning point for others having a similar problem.
It was mentioned in a different topic.
Someone suggested above that I check the ram did a membership and it was a sea of red errors