I leave the "best fan" to someone more qualified for your setup but after spending the last week searching for stuff I would like to suggest the best way is to go to pricewatch.com and check different vendor prices after you decide what you want. I found several good sites which were: Inflowdirect.com, crazypc.com, puicorp.com (power up inc.), coldcpu.com, and allstarshop.com (80mm case fans for $4) which I liked one of the best as they listed the mfg. website with the product so you could get tech info and more detail as needed. A lot of posters seem to like Alpha, globalwin, and toms hardware review liked the swifttec best in these <A HREF="http://www4.tomshardware.com/cpu/00q4/001211/cpu_cooler..." target="_new">tests</A>(thanks bnn). crazypc is getting the heatsink in soon (its pricy)and crazypc and inflow direct have the arctic silverII for less than $9 bucks. Good luck and beware of information overload!
Most of the heatsinks and fans should be able to cope with an 800 clocked to 1000 fairly easily. It is when speeds start getting above 1000mhz that you should be more concerned about the quality of the heatsink and fan. I tried several Coolermasters heatsinks, the Global Win FOP38, the Copper Hedgehog with Delta fan, and the Alpha PAL6035 with the Sunon fan with results that did not allow me to overclock the CPU any further. For instance, with my 900mhz TBird, the max speed the CPU could handle was 1066mhz with the occasional lockup, 1050mhz was stable. No matter what Heatsink Combo I tried, cooling it to 29C at idle and 38C max under load, did not help any at all in achieving greater speeds. All heatsinks allowed the same exact speeds on the CPU, but just lower temps in doing so. The temperature did not effect the performance any, it just happened to be the limit of the CPU. I image the only thing that would have gotten the CPU clocked higher would have been more voltage than the maximum 1.85 Volts the board can supply. My 1.2Ghz CPU clocks to 1.4Ghz, fairly stable, but again the occasional lockup. At 1370mhz it runs just fine with no problems. Again, no matter what heatsink or fan I tried, the maximum speed of the CPU remained at 1.4Ghz being slightly unstable and 1370mhz being stable. The only thing is that the Heatsink needs to be albe to maintain the temps under full load. If the temps keep climbing and climbing, than a better heatsink, and or fan is in need. I currently use the Alpha PAL6035 with Sunon fan. This setup produced the least amount of noise, good temps, slow rise in temperature under full load, compared to quick increases with the Coolermaster heatsink I tried, and fairly quick cool off when the load on the CPU was removed. I use Arctic Silver, but to be honest I have only seen a 1-2C change in max temp. One place the Arctic Silver compound may be beneficial is in the slow rise in temp and quick cool off I have noticed due to the Arctic Silver compound allowing for a better transfer in heat. I have rambled too long, later.