Depends what you mainly use it for, Jam. What you have is a pretty good spec already. I'm not 100% convinced that you would see all that much improvement, in general terms, by upgrading, but others may disagree. My PC is about 18 months old now, and I have built others for other people, with similar specs to what you have, (higher than my own) but I haven't really noticed a 'WOW!' factor with the new ones, compared to my own.
I suppose it's because I mainly use mine for Internet, which is only as fast as the connection, but a gamer would probably notice more of a boost in speed following an upgrade.