For clarity the 3800+ has a 10x multiplier and is therefore operating at 2Ghz stock speeds...the 165 has a 9x multiplier and is therefore operating at 1.8GHz
Despite what many will argue, clockspeed is a much more important factor than cache size. If you were to compare a stock 165 to a stock 3800+ I believe you'll find the 3800+ to be faster in most everything, simply due to the fact that clock cycles are what determines IPC rates and cache size is simply a high speed memory access point.
That being said, overclocking can correct the IPC differences between the two and having larger 1MB cache is most certainly a nice bonus