Hi, I've got an 8,1 iMac with 4GB of RAM and a 320GB hard drive (WD3200AAJS). The HD is getting full and the system is really slowing down, so I'd like to upgrade it. I've noticed that s few of WD's HDs on OWC come with "6Gb/s 64MB Cache" while most, including my stock model come with 3GB/s 32MB. I'm specifically looking at the 1TB WD1002FAEX model which goes for about $99. My question is, how much do either of these attributes really matter; and can my iMac even use the extra speed they offer? Are they worth saying "I'm not going to consider anything below that?" Also, I've always found the easiest way to swap out hard drives in a MacBook was to purchase an enclosure and use Carbon Copy Cloner. Enclosures for 2.5 SATA are abundant, does anybody have any recommendations on ones for 3.5? Thanks.