DDR3 for my Asus P5E3 Deluxe

[GPS_Flex]

Hi, newbee here (first post). Very nice website and forum.

I'm building my own computer for the first time and I'm at a point in the process where I need to buy my DDR3 memory. Here's my build so far:

Cooler Master Cosmos S Chassis
Asus P5E3 Deluxe MOBO
Intel QX965O CPU
2x 150GB Raptor X HDDs
Enermax Galaxy 1000 watt PSU
Windows Vista Ultimate (64 bit) OS

I'm leaning towards going with 8GBs (4x2GB) of the Patriot Extreme Performance Viper Series DDR3 PC3-12800 Low Latency DIMM Kit because I can't find anything else that comes in 4GB kits and gives me the full 8GBs possible with my mobo. Here is a link:
http://www.newegg.com/Product/Product.aspx?Item=N82E16820220285&ATT=20-220-285&CMP=OTC-P12ice5can&nm_mc=OTC-P12ice5can&cm_mmc=OTC-P12ice5can-_-Memory+(Desktop+Memory)-_-Patriot+Memory-_-20220285

I'm also looking at some of the "faster" memory that is available (example) http://www.newegg.com/Product/Product.aspx?Item=N82E16820220300 with less memory and less cost.

My question is this. Should I buy 8GB of the 1600MHZ DDR3 memory or should I buy 4GB of the 1800MHZ DDR3?

[Apoptosis]

What will you be doing that needs 8GB?? I have 12GB in one of my home servers and can't get half of it full.

[GPS_Flex]

I'm running (Auto Desk -Auto Cad) Land Development Desktop with 3" (ground) per pixel photogrammetric images in the background. These are high resolution aerial images/tiff files that are xrefrenced into the program. I also do some 3d rendering from time to time.

I'd like to play games (at the highest level of perfomance possible) when I'm not working too. I own Crysis and similar games and play them when I'm not working or reasearching how to build this computer "the right way".

[Apoptosis]

If you think you would need 8GB then I'd suggest going with that rather than a kit with less capacity.