Updating your hardware has been addressed in these forums many, many times ... still, here's my take on it:
Use Norton Ghost to copy your existing setup to your new hard drive. Ghost will offer to expand your partitions; I'd leave "/boot" the same, expand the swap space to twice the RAM in the new server, and let the remaining partition fill all the rest of the new drive ("/").
Then boot the machine from whichever CD you like ... since you have add-ons I'd probably stick with 5.6 ... do an "upgrade" install then re-apply all the Update 5 RPMs. You should be in good shape. If something goes wrong, you still have your old install and can re-Ghost.