1, The ocuk stuff is all well known makes its just whatever they buy in bulk or get a deals on, for eg i have ordered about 3 ocuk gfx cards in about 3 years and one was msi 8800gt, one was a pny gtx 260 and the 480 gtx i bought and have now is made by sparkle.
2, as for the hdd you wont notice any performance hit by not having 64mb of cache and as for 6gb/s the most a 7.2000rpm hdd will do is about 130mbps no where near the bandwidth of sata II (300mbps) and even further from sata III (600mbps)
3, the xfx range as far as i know is one of the best you may have just seen a few bad reviews and like i said they are made by corsair anyway which you were going to bye
4,unless your a mad overclocker the memory timings wont make a difference save the money and get the better gfx card