For your information, I have a PowerPC G4 computer. I also have a PC, but I do use Mac more often. Almost any parts can be replaced too as well, in fact I've already done that. However, for the eMac and iMac, I don't know but I know several parts can be replaced. Though, I don't know about the ethernet. Actually, there are many PC computers that are built in a similar method to iMac. It's the desktop computers that I prefer, not the all-in-one computers. All-in-one computers are for average joes, not graphic designers, video editors, or anything that requires a lot of power from a computer.
By the way, that CPU speed thingy.... completely a myth. RISC and CISC CPUs are designed in different ways and are designed to run differently too. So, there is a big difference between a PowerPC RISC-based CPU and an Intel CISC-based CPU (AMD too as well).
Believe it or not but it's true. Don't let the numbers fool you.
Actually, you can get the Civilization games including Civilization: Call to Power on the Mac. Mac computers often get the popular games too as well like Doom III, Wolfenstein, Rise of Nations and more. But I often reserve my game playing for the consoles with a few exceptions.
