Four years ago I bought my first 2-core processor, an Intel Core 2 Duo. It was the introductory model, the E4300 "Allendale", and is the slowest desktop Core 2 Duo that exists.
Being that I absolutely do not want to put cash into a whole new computer system, I decided it was time to upgrade the CPU to keep my computer box somewhat current. My motherboard has a 775 socket which is older now, but my board can still house a decent CPU.
The biggest decision I had to make was whether to buy another more modern Core 2 Duo or a Core 2 Quad. I thought for sure I was going to do with the Quad, but actually decided on the Duo; it should arrive next week.
When I compared the two side by side, the E8400 is better and is a significant upgrade from the four-year-old CPU I have now. The FSB is much faster, the cache is tripled, it will run about as cool as my old CPU does now and most important is better for what I do with a PC to begin with.
The sell was the cache and the virtualization tech. The Duo has 6MB L2 cache while the Quad has 4MB; it also has VT-d which will help out with the virtual PCs I run. What VT-d does is allow virtual computers direct access to peripherals instead of emulating it all through software means. The Quad only has VT-x, which is good but that in combination with VT-d is awesome for virtual PC stuff. For what I do for a living, I try out a lot of OSes and need every edge I can get, and the Duo is better suited for the task compared to the Quad. I might even finally be able to give my guest OSes the ability to directly access video memory for enhanced environments.
This CPU upgrade will be the last processor I install for the motherboard I have currently. When the time comes to move on to something better, it will be a whole new system. Hopefully I won't have to do that for another 4 years. 🙂