Keep in mind that if you download the updates from the update catalog you will likely end up installing them one by one and rebooting almost every time. A painfully slow process. Downloading SP1 would be a big step in the right direction if you don't have an integrated install disk. That would save you some time on windows update. I also like to download the latest DirectX full version, Silverlight (if you use it), IE 9, Dot Net Framework 4, etc, and save them to a thumbdrive. Microsoft Security Essentials too if you use it.
Another option would be to install Windows, all your drivers, and then hit windows update. Then when its fully patched, save an image of your hard drive with something like Acronis True Image. Then the next time you have to do a re-install just restore the image.