Indeed it was. I had unzipped the file via Finder (Lion). Turns out when you do it that way there is no trace of empty.bin! Once I unzipped via the command line, the file was there and I was able to reflash the card (yay).
Might be worth adding a note to the OP for mac users. I view this as a bug in OS X.
Thanks for your help I think I'm set.
Update - I've moved the 4 drives that were on my SAT2-MV8 to the new card and my initial parity check speeds have gone from 25 MB/sec to nearly 90 MB/sec. Huge gain, thanks much!
I'm abit confused, what Unraid version are you using? Is it fully compatible with this M1015 card?