Ummmm.... no
The A7M266 will run (with good memory and proper cooling) in the mid 140Mhz range for the actual FSB clock speed (I've seen one hit 148 and run rock solid). As a result of the DDR memory interface the _effective_ speed is in the 290Mhz range (DDR clocks data on both the rising and falling edges of the clock, so for example if the actual clock speed is 133Mhz, the memory is actually running at 266Mhz).
That aside, in the majority of programs today you won't see that large of a gain from DDR, with the exception of memory intensive programs (like say Adobe Photoshop
)
As far as cooling, temperature... electronics live longer and are more reliable the cooler (within limits) you run them. They will also operate at a higher speed the cooler they are (actual propogation delays inside the parts get larger as temperature goes up).
That being said, a _good_ heatsink/fan combo is a must for the processor itself. In the mid-price range I would say an Alpha cooler like the PEP66 or Swiftech's MC370. The best hs currently regardless of price for an Athalon is Swiftech's MC462-A.
Of equal importance is proper mounting of the hs/fan combo and use of a high grade heatsink compound. Artic Silver is what I would recommend for the hs compound.
As far as case cooling, it depends on what all is jammed inside your case. General recommendation, fans blowing in on the bottom, pulling out on the top. Keep things inside your case neat (wiring, cabling, etc.) so that the air can flow as cleanly as possible through the case. Almost all modern motherboards have temperature sensors. Use them, watch them.
Initially if your case has semi-decent cooling, you need make no changes and simply keep an eye on the temp. If you notice a heat buildup over time, then you can make modifications later. If you aren't picky about asthetics, you can even go the old fashion route...take the cover off and sit a 2 to 3 foot box fan blowing into the case next to the computer
