More more news:
Graphics card: If you can find Radeon X1900XT with 256 MB GDDR3 for around 150 pounds buy it. Sapphire model of Radeon X1900XT with 256 MB GDDR3 has the lowest price from all ATI vendors/manufacturers. ATI cut off prices two days ago and now Radeon X1900GT is not any more worth for buying. Not to mention how much more powerful is X1900XT. X1900XT with 256 easily beat new GeForce 7950GT model, not to mention 7900GT.

If you want to read tests of the latest graphics cards go here:
http://www.anandtech.com/video/showdoc.aspx?i=2827&p=1 (Fall '06 NVIDIA GPU Refresh - Part I: GeForce 7900 GS)
http://www.anandtech.com/video/showdoc.aspx?i=2833&p=1 (Fall '06 NVIDIA GPU Refresh - Part II: GeForce 7950 GT and SLI)

From test:
The single 7950 GT card from NVIDIA does not seem to offer a greater immediate return on your investment than its major competitors in the X1900 XT family. First, the X1900 XT 256MB is cheaper than the 7950 GT. Both flavors out perform the 7950 GT in multiple games. Where the 7950 GT does lead the X1900 XT 256MB in a couple cases, it never leads the 512MB version. Obviously, the usual exceptions apply and those shopping with only one particular game in mind may form different conclusions, but in our eyes, the X1900 XT series are still better deals than stock speed 7950 GT parts.
As I plan to buy new computer to the end of november, it will be definitely Sapphire Radeon X1900XT 256 MB GDDR3 as graphics card (if I don’t buy desktop replacement notebook).

256 or 512 MB video memory?
512 MB video memory is only important if you plan to play games in 1600x1200 resolutions or higher (like 1920x1440). As the most 19” LCD monitors have native resolution 1280x1024 so, there is no need to buy card with 512 MB. For higher resolutions you will need 20” or greater model of monitor which is the waste of money except if you are rich.

Motherboard: Also good model for Core 2 Duo in rank of ASUS P5B is Gigabyte GA-965-DS3. In rank of ASUS P5B Deluxe is Gigabyte GA-965-DQ6. The craziest thing about those models is that their owners in various forums have unofficial “war” in claiming which model is better: P5B vs. DS3 and P5B Deluxe vs. DQ6. In fact you can’t be wrong whatever model you buy. Just avoid MSI P965 models.

Hope it helped.