Where to buy RAM online or in greater JHB?

One of my (rarely used) workstation PCs has become susceptible to periodic hanging/ freezing and I've isolated the problem to the RAM.  I originally had 4x Corsair DDR2 CM2X1024-6400C4DHX 4-4-4-12 chips installed and through a process of elimination isolated one I believe to be bad and things were fine for around 6 months thereafter.  Now the pattern of behaviour is repeating so I want to go out and replace all the RAM chips.

Also, having just purchased a HP Proliant Microserver I'm looking to add 2x 4GB PC3 DDR3 RAM chips.

Kingston would probably do fine in both cases.

Any recommendations as to where to buy RAM online and take delivery or collect within the week?