Crucial ballistix sport DDR3 1600 8GB kit
 

As true as it was several years ago it stands today, the cheapest way to increase a system's speed is to increase the amount of ram up to a certain amount. The magic amount used to be 4GB and it seems to be increasing to around 8-16GB especially with Microsoft pushing 64bit. Fortunately Crucial has put out a 8GB sport kit with surprising results.

http://www.techwarelabs.com/crucial-...-1600-8gb-kit/