The latest in processor technology, quad-core, can be the hardest on your wallet. A 2.3GHz processor alone will cost around $130, but a 3.2GHz processor can cost anywhere between $800 and even up to $1400. Quad-core is useful if you’re planning on stacking your computer up with more than 4GB of RAM and over 1TB of hard drive storage.
As always, if you're interested in upgrading to quad-core, make sure that your computer can handle it. Otherwise, quad-core should only be considered if you have a brand new computer or are building your own machine.