Where does it say 2.6(350)? ... Go to the Apple menu and choose "About this Mac". There it should say something definite. PCI graphics probably mean it's a 350 MHz "Yikes!" PowerMac G4. The iMac certainly sounds like the better deal. You'll want the OS X license to be "good", though. Installing from an installation disk that came with another Mac is not a good idea in various ways. (Steve would probably say "Karma".)
Mac user since 1987. Running Mac OS X 10.8 Mountain Lion on a MacBook Air 11" & an iMac 27" and whatever's newest for my iPhone 4s, iPad 3 and AppleTV 2.
Apple Certified System Administrator 10.6, Apple Sales Professional 2008-2011, Apple Certified Mac Technician.