I can't see the proposed specs, but I also started planning my 'Christmas' computer around August of last year and can offer some buying advice.
I think most folks are right that you shouldn't even think of buying the processor or video card at this point - prices/technology will be vastly better in just a few months time for these componenets.
That being said, I think it makes sense to start looking for hot deals on things like cases, power supplies, RAM, and CDRW/DVD drives. These components aren't subject to "Moore's law" type impovements, so if you see a good deal now, I say jump on it.
For example, I picked up a 32X Lite-on (Cendyne) burner from Staples last week for $15 delivered. I know I'll be perfectly content with this come December, even if they come out with 58X burners between now and then. Also, look for sales on cases/power supplies at Best Buy/CC/CUSA etc. These go on sale every couple of months, and you can save $30-40 there. RAM prices fluctuate unpredictably, but Circuit city/office depot/etc have been offering 256 meg DDR sales for around $25-$35 recently. I'd jump on these now - even if RAM prices drop to free you're only out $25, but it's quite possible RAM could be going for $100+ come christmas.
Just my $.02. Good luck with the build.