wow, looking at my last post i can tell that i need to lay off the alcohol... anyway, i see you are looking into DDR. from the reviews i have read, the alimagik1 chipset so far has sub-par performance. the amd760 chipset seems to be the best with the kt266 running neck and neck. if you want DDR, i would personally suggest that you wait a month or two (i know, the upgrade bug has cought you) and let the kt266 chipset mature a bit (and perhaps drop in price). amd isn't really in the chipset market...they seem to introduce a chipset and then let other companies perfect it, like via. the msi k7t pro266 (with the kt266 chipset) and the asus a7m266 have received good reviews so far. the last few msi boards with the kt133 and kt133a chipset have proven themselves to be winners and asus has had a long standing reputation for making quality motherboards. if i were going to buy a DDR mobo (and i might soon) i think i would go with the msi (even though it is a bit more money than the soyo you mentioned). ok, next topic...you ask if the duron 750 would be "easy to overclock to 1ghz..." and the answer is...do you feel lucky? as i have said earlier, there is no guarantee or "easy" when it comes to overclocking. as an educated guess i would say that the duron 750 will "easily" reach 900mhz on a board that allows for overclocking. furthermore, i would bet that you can reach 1ghz...but don't hold me responsible if you don't
get my point? now for cooling...in my experience the orb's aren't very good. i would go with an fop-32 (the fop-38 has a better fan but is MUCH louder) or a good taisol, like the CGK series (i like taisol personally). remember, a good socket-a hsf will carry you through future socket-a upgrades and overclocking adventures. the same holds true for your question about the power supply...i would NOT get less than a good brand 250 watt power supply. a good 300 watt is definately recommended though.
i almost forgot to mention this!!!!!!!...
if you buy a DDR motherboard with pc2100 ram, you are going to want to run your duron at a 133mhz fsb (which is effectively 266mhz because of the athlon/duron ddr fsb). there are no duron's that are sold to run at a 133mhz fsb (only the athlon "C") therefore you are going to have to try to run your duron at at least 6x133 or 798mhz. now, it will probably work but i can't stress enough that there are no guarantees!
ok, i'm surprised you are still reading...your choice of crucial ram is a good one and 128megs should do for now (i suggest a total of 256megs if you can afford it).
as for your last question, i have never ordered from mwave but i have only heard good things about them so i can't say anything bad.
i wouldn't be surprised if i confused you more than helped you but i did my best to answer your questions...if you have more questions, ask again and i will try to help if i can