A 3GHz P4 is the most expensive I think anyone would want to spend. If you already have an Intel CPU at around 3 GHz, there is little point getting a 3.4GHz one.
Wait a while if you have the money to spend on a 3.4GHz P4. Intel will come out with a better CPU with 64-bit extensions like AMD. AMD will surely have something really great by that time.
A 3.4GHz P4 is just not worth the money right now.