Thats entirely up to you. If your happy with it...then dont change a thing. If your looking for more...Then by all means shoot that soothing drug we call "upgradeitis" in your veins and hold on for the ride!
couple of questions for you:
What are the model numbers of your speakers?
What kind of budget would you be will to invest?
Is this for home theater or music?
Any restrictions...room size, parents, significant other, rent/own your home/ appartment?
Do you need more inputs?
do you need new technology...HDMI, Firewire...?
It sounds like youve got a good start. First I woulld decide what the weaknesses are in your system and then decide if your are willing to invest in upgrading.
