i series use different sockets.
When overclocked the Q6600 is still a nice CPU. I don't think that anything you could upgrade would give you enough performance increase to make it worth the expense.
PSU died because
1. Inadequate capacity,
2. Inadequate quality, or
3. Just a random failure.
If you had posted PSU specifications, we could make an educated guess.
Overclocking: This is why, for CPU's, we all say, "Learn to use the BIOS". For GPU's, you have no choice but to use a Windows utilty. I do not like overclocking video cards. They tend to run hot enough anyway.
HundredIslandsBoy:
The paperclip trick is not really that useful. If the fan doesn't spin up, it's dead - or there's not quite enough load on it. If it does spin up, all you really know is that it produced enough power somewhere around 12 volts to run a fan. Now, if you have a DMM or a PSU tester, it's a little better. You can check all the voltages, but you still do not know if it will support the electrical load of a computer.