What are you using it for? These *are* 5-year-old systems, keep in mind. For things that don't use an absurd amount of RAM and/or have fewer than 6 threads, a single modern multi-core CPU will be faster. Dual 6-core Opterons (can be had for fairly cheap; check out HP XW9400 for a platform) would also probably be faster for many things. Adding a modern GPU to these rigs will give a significant performance increase for non-crunching tasks but again, these are 5-years old. Myself, I'm doing it for the challenge! Even if it's slower than my overclocked Core 2 rig (which it will be for some things), the challenge and satisfaction of the project is worth it for me. YMMV