If you are thinking of going the Route of mini+external display, I would think about maybe looking into non-apple displays. Yes, the cinema displays are nice, but they are also overpriced for the average user. You might be able to shave another couple hundred off by getting a different display. Another thing you might want to look into is the cost of getting a PowerMac G5 and an external display - you might extend the life of your computer a good amount if you go that route, and if you decide to replace the unit you don't have to incur the cost of a monitor again.
MP
MP