Hi, I'm looking to replace my iMac's hard drive as the current one is painfully slow. I'm keeping all my media (the majority of my data) on an external HD so that I can use it with my Macbook or iMac. Consequently, I don't need much hard drive space at all, so I was going to buy a SSD and maybe add a second HDD to replace the DVD drive. I'm going to get one of these SSD (with the adapter): Crucial MX100 128GB - $70 Crucial M550 128GB - $85 Crucial M500 240GB - $90 Is there a relevant difference between the MX100, M500, and M550? If there are speed differences, given that my iMac is SATA II and not SATA III, are the speed differences really relevant? Additionally, is this OWC kit on Amazon sufficient (or overkill) for the iFixit replacement project? Also, if I choose to swap out the optical drive for another hard drive, is the PATA Optical Bay Hard Drive enclosure the only other thing I'll need to buy (aside from another HDD) for that project? Also, does it matter whether that HDD is a 7200RPM or 5400RPM HDD?