A failing power supply can cause many mysterious problems with your machine, like program instability, random reboots, lockups, etc. 200 watts is a bit low, especially if you are using higher-end parts. I can't say you're going to damage your parts this way, but its never a good idea to put more draw on your PSU than it can handle.
Try downloading
Motherboard Monitor or other monitoring software, and check your voltages. Make sure they are relatively stable (ie: don't fluctuate more than .1 or so away from what they should be, like 3.3, 5.0, and 12.0, on their respective lines).
But if you are not experiencing any problems, then perhaps its handling the load well enough... don't fix what's not broke, I say (unless you don't mind spending the cash on it).