Well, according to the following benchmarks, the i7 blows away the e8400 in terms of performance.
http://www.cpubenchmark.net/common_cpus.html
I know that's not the overclocked specs, but still. The i7 could be overclocked to be even better, am I wrong?
Also I was looking up some RAM... There's the exact same RAM but with 400mhz difference with a 30 pounds difference... is that extra mhz worth the 30 quid?