not to be mean or anything but could you please STOP making threads about the same subject just keep it in one thread. also to answer your question it is worth it to spend the money on the game if your willing to. its all up to you though. upgrading will improve overall system performance.
If you are going to upgrade for a game, do it for Crysis. That way, you will be able to play just about anything that releases for quite a while. (That includes Oblivion ).
I personally don't think it's wroth buying a new processor/memory for one game. find at least 3 games you will enjoy playing on a higher end system, then do it...