A New Computer

but as time goes on it's going to take 4 Gigs just to fire up the OS

No it's not, unless you have totally hosed your system all to hell, and are running a ton of apps at startup.

If you just installed Win7 tonight,, you need to give it time, it will settle down after a few days and a few reboots.
It is doing stuff in the back ground, then check memory usage...

Keep in mind that Win7 is not XP and handles memory differently, let windows manage the memory and page file and don't worry about it till you start seeing real issues like memory leaks from apps.

Personally, I still will not see the need for any system that is not used for Many Many Heavily used Virtual Machines, or CAD or Some other memory heavy apps to need more than 4G of memory. Even in 64bit. If all you are doing is gaming and simple video/audio/image stuff, then you still won't need more than 4G. You will be wasting your money.
Put that saved cash into a better video card and/or SSD. That will be better money spent.

as a side note,, keep in mind that games are off loading their graphics to the GPU's, not the System Memory.
Even some Video Rendering and Imaging apps are utilizing the GPU rather than System memory.
Which is also why there is a growing concern over Viruses that infect the GPU instead of the system hardware.

To my knowledge, and I could be wrong, no AntiVirus around scans GPU memory or processes.

GPU virus - Bing

You will find that a top of the line GPU (or even a slight upgrade) will run games way better than a mediocre GPU and a lot of system memory.

They are taking advantage of the over all GPU (right, no longer really referred to as a Video Card other than a nostalgic reference to the GPU in general).

Yes, you will, for some time to come...... by the time you really are interested in a memory addition, if it will even be needed,. ,, you really will want to build a new system. I suggest start saving now.