Should I upgrade my iMac G5 to the newer model?

Should I upgrade my iMac G5 to the newer model? I’m running low on hard drive space, I’d like to have more RAM, and I want a graphics card that can actually play more complicated games like Half-Life 2. From what I’ve heard, I can’t upgrade the graphics card on a G5 iMac, and I can only have 3GB RAM, (what I have right now), and it comes with a much better graphics card. Oh, and I guess the new HD widescreen 27” display looks kind of cool too. :-P