Memory 'used' means used by applications. This should be about 5-25% of your total RAM. The vast majority of your RAM should be available as filecache. This will allow applications you used since the last reboot to be cached in RAM memory. Therefore, you have three kinds of memory usage: used for system/application, available but used as filecache or free and unused memory.
If you use SSDs, the extra reads caused by having very little filecache should not interfere with your desktop experience too much since the SSD is not that much slower than your RAM. But even so, more memory might smooth out things. Especially since 32GiB today is only about $150 for a cheap kit. I see you are an overclocking fan, but as a general rule RAM quantity is superior to RAM performance, especially in relation to disk performance.
When building a newer system (Haswell?) you could opt for the 16GiB DIMMs coming available just now. By having 2x16GiB, you can upgrade to 4x 16GiB in the future. That much RAM is simply great and future operating systems would make good use of it. Such as Linux and BSD with tmpfs, Microsoft should wake up at some point as well.
If you use SSDs, the extra reads caused by having very little filecache should not interfere with your desktop experience too much since the SSD is not that much slower than your RAM. But even so, more memory might smooth out things. Especially since 32GiB today is only about $150 for a cheap kit. I see you are an overclocking fan, but as a general rule RAM quantity is superior to RAM performance, especially in relation to disk performance.
When building a newer system (Haswell?) you could opt for the 16GiB DIMMs coming available just now. By having 2x16GiB, you can upgrade to 4x 16GiB in the future. That much RAM is simply great and future operating systems would make good use of it. Such as Linux and BSD with tmpfs, Microsoft should wake up at some point as well.
