Why are you so worried about WPA, it's here to stay so get over it. Like you said yourself you have yet to perform any upgrades so why did you say i would encounter problems when you have not even...
On the fly (24X) my CPU usage is 1% and burning from the HD the CPU usage is 3%. If you are hitting 100% and its staying there you are either using a slow CPU or your PC aint set up right.
My 1.4GHz T-bird hits 60c at full load on a regular basis and my PC is stable as a rock. Those temps are fine mate dont get all hooked up with spending loads of cash trying to shave a few 0c off.