Yup, good system with some decent RAM.
Your RAM is currently running at 1333MHz, which is great and any extra MHz on top of this won't really add much extra performance (since the sandy memory controller is really very efficient). However, if you paid of 1600MHz RAM or faster then you may want to apply the rated RAM settings in the BIOS.
As for 4GB being enough, for general tasks it is usually plenty. Also, most games are only 32 bit - so they can't make use of more than 4GB RAM.