Intel Pentium 4 551, Pentium 4 541, Pentium 4 531, and Pentium 4 521: Intel offers a handful of other Pentium 4-based single-core CPUs in this category. The Pentium 4 551 runs at 3.4GHz, the P4 541 runs at 3.2GHz, the 531 runs at 3.0GHz, and the 521 runs at 2.8GHz. Each has 1MB of L2 cache, Hyper-Threading functionality, and 64-bit support. The prices range from $300 for the 551 to $180 for the 521.
AMD Athlon 64 3500+, Athlon 64 3200+, Athlon 64 3000+: AMD offers a bevy of single-core Athlon 64 processors in the mid-range. The Athlon 64 3500+ runs at 2.2GHz and features an L2 cache of 512KB. The 3200+ and 3000+ also have 512KB L2 caches and run at 2.0GHz and 1.8GHz, respectively. With larger L2 caches, Intel's mid-range Pentiums beat these CPUs in Windows office application performance, but they also cost slightly more. The 3500+ can be found for around $275, while the 3200+ and 3000+ cost only $210 and $150, respectively.
At this range, you get what you pay for -- which isn't much at the bottom end of this set of CPUs. Our recommendation: If you can afford it, go with either Intel's or AMD's dual-core offering.