Processor selection can be summed up in three P words: performance, power and price. Performance comparisons can be found in our CPU Charts, price comparisons in our Customized Pricegrabber Search Engine, and TG Daily even does an occasional Price to Performance Comparison. Power consumption analysis requires a more thorough reading of our CPU Reviews.
At the present time, very few applications are able to set apart Quad Core desktop processors - such as Intel's recently announced QX6700 and soon-to-be-released AMD models - from dual-core CPUs. Anyone looking to "stay ahead of the game" might still choose the latest and greatest Quad Core, but those who value their money might prefer to wait until the next upgrade cycle.
Enough applications have been optimized for dual-core chips that these should be considered for any moderate to heavy use, especially when multitasking. Intel Core 2 Duo leads here, but the AMD Athlon 64 X2 provides good value in sub-$200 models.
Single Core AMD and Intel models are still worthy of consideration for low-budget systems where performance is not a priority. Lower model AMD Athlon 64 and Intel Pentium 4 models are available for well under $60, while the cheapest AMD Sempron and Intel Celeron D versions can be found for less than $50.
Power consumption is a major concern for low noise systems, because increased cooling needs usually require higher fan speeds. The latest generation of Intel and AMD processors has made great strides in performance per watt used. AMD also offers even more miserly Energy Efficient and Small Form Factor versions of its Athlon 64 and X2.
Finally, Mobile on Desktop platforms might be the ultimate expression of silent computing technology, allowing ultra-efficient notebook processors to be used in desktop enclosures. In fact, these tend to be so miserly as to allow small coolers to operate well below ambient noise levels.