If it was in the same generation, it would mean a little, but the i5 3450 is a much better and faster CPU overall.
This isn't an exact comparison because it's a 2500K
(about the same performance at stock as the 3450 because of the 3450's slightly
better per clock performance, despite a slower clock speed) against the Q9650, but it gets the point across. http://www.anandtech.com/bench/Product/49?vs=288
I DO agree with amuffin, though, if you already have the Q9650, just wait for Haswell.