Video cards dont... cut mustard..
Besides that, I can tell you that right now is an EXCELLENT time to put a computer together, and Waiting until December is not a bad idea. Since I built my rig (for around 1500 dollars) prices have only dropped. Prices are at incredible lows, if you know where to look (Newegg is NOT always the best option.. well it's the best option if you want your stuff shipped quickly).
As for "future-proof" .. good luck. New things are coming out daily. What you need to consider with your build, is "ADAPTABILITY" and why I mean by this, is instead of making a FUTUREPROOF build, its basically FUTURE RESISTANT.
You want lots of headroom to upgrade. This means mobo's capable of 8gigs ram, 775 slot is where Intel chips are going to stay for a long time, so it has to have one of those (I'm assuming youre going intel, seeing as how you are posting in the intel forum >.<). You want plenty of SATA ports, since IDE is officially redundant (feel free to argue, but it's true. IDE is bulky, cruddy, and does not have the speed capability of SATA and SATA II. One day HD's will go at 3.0Gb/s).
You will want multiple PCI-E slots, possible PCI-X.
As for VideoCards, 8800 series is an amazing card and will be relevant for 5 years at the least. No fear buying one of those.
Everything else you get for your computer will be very adaptable. RAM, Drives, Hard Disks, Mouse, Keyboard, Monitor, they will all last you a good 4 to 5 years provided you dont break them.
So I say now is as good a time as any to buy the parts for a computer, but if you wait a few months, prices will drop on the high end stuff right now. The 750GB hard drives will drop from 250 to like 150 dollars, and various other prices will drop 25 - 35 dollars.
It's all about, do you want it now, more expensive, but you get 4 months of enjoyment out of it and more? or wait, and save a few dollars.
I say GO NOW. Gotta walk before you crawl.