I had a Q9300, and than upgraded to some i7 because I needed more slots on the motherboard. I was very surprised by how much quicker the whole system was, even if I was under the same impression, that in the last years things didn't change a lot.
CPUs get faster by around 20% per year, but in 8 years this can get compounded a lot.
this is very very different from back in the 90s, in those good old days 18 months old PC is basically useless.