I am in Australia and from what i know of newegg they do not ship international, it may have changed since I last inquired.
1G of ram will be fine with XP and the same with going down to the 1.8 dual core if you need to shave some dollars off.
The only thing I might do if it is running 24/7 is to add a fan ( looks like the case will take an 80mm one on the side ) that will help increase air flow. From the pics I can not see if it will take a front fan or not but if it does I would get one. Running 24/7 is not really an issue. I run one of my computers 24/7 for a couple of years without failure and only rebooted it every now and then.
One thing to remember if it is running 24/7 is to keep an eye on dust buildup, as dust builds up heat increases as dust seems to be a good insulator, A can of compressed air does wonder every now and then
Ohh one other thing, if you are going to run 1G then you will have to get 2X512mb sticks for your ram to run in dual channel mode
http://www.ebuyer.com/product/125136
Also you have the option of ditching the motherboard and video card i suggested and going something like this with onboard video. If you are not going to do ant graphics intensive stuff like games , onboard video will work fine.
http://www.ebuyer.com/product/132097
you can save another 33 by going that route.
one thing I wouldn't cut down on tho is the power supply, considering you will be looking at 24/7 operation