As for the mobo, well, I feel that the lack of the following features will inhibit your potential to over clock successfully:
1) No RAM voltage control
2) No chipset voltage control
3) No support for RAM greater than pc3200
I feel that its support of dual 12v rails are a plus when over clocking requires greater accuracy of power distribution. Personally I think the mobo will serve you adequately for a low-level beginners over clocking adventure, but if you are experienced, this board is a no-no.
As for the memory, yes I agree that you should buy one more stick of 512mb pc3200 so you can get the dual channel option working with your pc3200 ram (make sure its the same brand). I also feel that you should sell your pc2700ram on eBay and use the money to buy more pc3200 ram (of the same brand) because the general opinion is right: mixing different quality ram will just cause all sticks to run at the slowest speed.
Your CPU is a great choice because of the low vcore and high 1mb l2 cache. Good choice and it will serve you well in over clocking potential. The stock cooler won't be enough to handle the over clock IMO (mainly due to increase in frequency not voltages), so again, it was a wise choice to buy aftermarket cooling.
Your power supply is good; it gives ~ 34 amps divided between 2 12v rails, which imply greater compatibility with future devices. Unfortunately, that power supply is P4 optimized and not AMD optimized so you may not get full efficiency for your AMD unit. Also, it doesnâ€™t appear to be PCI-E compatible; I have not read anything about it supporting an independent 6-pin power connector that is required for your x1800xl to function properly (it plugs right into the card). You may need to buy a new power supply to be able to run your video card properly.
As for your after market cooling choices... any after market cooling solutions are breathtaking and extremely efficient. It is the one field of hardware design that can combine elegance and science. Your choices are good ones. I would recommend purchasing an aftermarket cooler for your card, choosing between the Accelero X2 and the Zalman lineup. From personal experience, my Accelero X2 has dropped my video card temps by 10 degree Celsius on idle and when I up the vcore form 1.075v to 1.25v and the vmem from 1.889v to 2.25v; I never get temps above 60 Celsius under load! Again, any after market cooling is a good choice to protect your investment. You've made a wise choice there.
Your hard drives, although dated, yes, will serve you well as long as they have 8mb buffers and not 2mb ones. I say this because as long as you use eide cables and have good udma 133 transfer rates, the performance of the drives will not inhibit your game play due to the huge amount of ram you have. Now if you had 512mb ram, like me, you will be gritting your teeth every time you hear a game needs 1024mb of ram to run because you know your system can handle it, but your load times will be excruciatingly frequent. The point I would like to get across is that SATA drives are not necessary for people who have >1024MB RAM dual channel and ATA UDMA 133 drives with 8mb buffers.
1) Get a new PSU that is PCI-E compatible. SLI compatible is not necessary.
2) Buy an aftermarket cooler for your videocard. (Don't forget to use Arctic Silver 5 )
3) Sell your pc2700RAM on eBay and buy another identical brand 512mb stick to get dual channel support.
4) Gte a really cool game like Oblivion and play until your eyes pop out
I am off to do that right now.