We need to know what the uses of your system is going to be for, so we know how to address the advantages, if any.
Gaming - No Advantage Really
CS5 - Multi-threading CPU (8 virtual cores vs 4 virtual cores), Triple-Channel Memory (1.. Higher Bandwidth [though only a slight improvement], 2.. Large Memory Capacity on Motherboard)
Games, software development, MS Apps, net, etc. I was able to get an i7930 chip from a friend for the cost of an i5 chip. I was not anticipating the extra costs of the mobo and memory so I'm trying to figure out my benefits of having an i7 chip and latest mobo is going to benefit me now or in the near future (2-3) years.