Intel's snazzy new CPU architecture again proves very potent. As you've witnessed, the Core 2 Duo E6300 generally got the better of this comparison in terms of performance. The E6300 is faster than the EE SFF-and, by extension, any of the three versions of the Athlon 64 X2 3800+-when running at stock speeds. When overclocked by an easily achievable 25% to 2.33GHz, this CPU can run with a AMD's fastest processor, the Athlon 64 FX-62. That's pretty darned spiffy for a processor that lists for under $200.  The E6300 doesn't draw much less power than the higher models of the Core 2 Duo, making it arguably less energy efficient than those chips. Still, the E6300 is easily more efficient than a Pentium D or a regular Athlon 64 X2.

Also, outside of a few exceptions, the E6300's smaller L2 cache doesn't handicap it significantly in terms of clock-for-clock performance compared to Core 2 Duo processors with 4MB of cache. What that says to me is that there's no reason to fear grabbing a 2MB version of the Core 2 Duo if you plan to overclock. You're not likely to miss the extra cache.

In short, if I were building a PC today and I could get my hands on an E6300, I'd grab it and go to town on the overclocking. The only reason I might hesitate would be worries about my motherboard taking the front-side bus beyond 1333MHz without problems. If you aren't confident about taking the front-side bus into the stratosphere, the higher multiplier in the E6400 might be worth the extra money. Beyond that, the E6300 looks like a killer CPU for an enthusiast's desktop PC.