Time for a new computer?

I am feeling it's time for a new computer. I can't precisely choose what I want to replace it with, but tonight I came across an article that caused me to look up some old details about my current setup. My screen was acquired in October, 2001, for $2500.00. The Apple Cinema Display's price had just been slashed from $4000.00, so I bought up the same display for a sweeter price. That's right, today I use the same screen. It still looks and operates great. The only thing wrong with it is the resolution isn't as sharp as some of the newer offerings. I estimate that I've put between 10,600 and 21,300 hours on the display. That's a big discrepancy, but my guess is it's right in the middle: let's say 15,000 hours. I've owned the display for over 2500 days, and I've figured the cost per hour, when I divide the cost of this thing, is around 18-19 cents. That seems high. But $2500 was a lot of cash in 2001 for a monitor. My PowerMac G5 tower has not been my favorite computer. When buying it, it required two trips back to the Apple Store for repairs. They ended up replacing the power/cooling unit more than once, and eventually, the entire motherboard. Ouch. Thank goodness for warrantees. This is the first desktop computer where I purchased AppleCare. The computer to this day is awfully loud. The fan constantly goes up and down and the slightest thing to keep cool. In contrast, my work computer, a Quad-processor G5 tower, is quite quiet. From what I detected at the Apple store, the current crop of Intel-based towers is likewise very quiet. The computer at the time cost me $2999.99. I am confident i no longer need the fastest thing Apple puts out for my hobbies and such, but I need something fast. So, I made up a little comparison chart. Click it for a full-size version. Surprising, perhaps, is that the quad-processor machine I have my eye on is about the same price as the dual G5 from 2005. I then compared the price of this machine against Apple's fastest iMac and their fastest MacBook Pro, with the legendary 8-hour battery. It turns out the laptop isn't value priced, but check carefully. For $2869 you're getting almost 3Ghz with 1920 pixels; the iMac is a value for a little more speed and the same number of pixels... at about 800 less. I am using my current Mac as a workstation and a media server. I had planned on using the new computer in the identical capacity, but I have to now consider what to do with the old machine. Sell it? Keep it as a media server (i.e., iTunes)?