I've upgraded several times to new versions as they came out. Latest is 2005. I am happy with the operation, the updates, and the stability of the software.

With the hardware you have, I don't see why you would be worried about the amount of memory needed [g].

Keep in mind that you don't have to upgrade the version of the Norton software when your update subscription expires... you can continue to use the same s/w and just purchase another year of upgrades.