WPG is a bit of an archaic measurement. Most reefers now refer to intensity of light in relation to depth of penetration in the aquarium.
In general, PC lighting is on the low end of the intensity scale. If you have any substantial depth, you will have a tough time keeping any moderate light demanding coral at a depth greater than 20" (however some will say less).
If you give us the dimensions of your tank, we may be able to give you a better idea of what you can keep - as I'm sure this is your main concern.
But, as a rule, you can expect light intensity as follows (from lowest to highest): Compact Fluroescent --> Power Compact (PC) --> T5HO --> Metal Hallide.
Now, I'm a T5 guy, but I will admit that MH is a fair bit more intense and will be more consistent PAR (unit to measure light intensity) throughout the whole water column. However there are some fabulous SPS tanks that use t5 only (like mine when my frags grow out
) and don't need MH to thrive.
With PC, you should be able to keep most LPS and softies but you'll probably have to step back from clams and SPS unless you want to upgrade.