Unfortunately, it's not possible for the speaker to be disabled during the startup process (initial beep occurs before the card's firmware is loaded).
But you can put a peice of tape over the hole to quiet it down noticably (also the easiest thing to do). You can also de-solder it from the board, but it is useful to have (alert when a failure occurs, so long as you don't disable it in the card's firmware).
I'm not sure this would work (alignment issues, particularly the ability to get the second SATA port attached).
I went and checked MaxUpgrade's site again, and the 8x SSD Kit for the Optical bay is still there (here). This would be the best way to go if you need 8x 2.5" disks in the MP.