Typically single-processor 1.6GHz or 1.8GHz models. Often sold "as-is" or without hard drives.
Rare "Quad Core" or high-clocked 2.7GHz models in pristine condition, sometimes including the original keyboard and mouse which adds significant value to collectors. Top Recommendations for Buyers
Buying a Power Mac G5: what to watch out for : r/VintageApple