SYSTEM DESCRIPTION:
Windows 32bit Home Premium; ASUS P5N-E SLI; E6600 with Artic Freezer Pro 7; Corsair DDR-2 XMS 2x1GB; Corsair 750W PSU; Raid 0; SATA HDD's; Apevia X-Cruiser Case; 120mm exhaust rear; 80mm exhaust top; 2x80mm intake front; 80mm intake side; Antec GPU slot cooler. BFG 8800GT OC 512MB.

I have OC to 2925 Mhz on the chip leaving DDR-2 at 800.

Memory Timing: Corsair CM2X1024-6400 2x1GB
tCL = 5
tRCD = 5
tRP = 5
tRAS = 18
CMD = 2 clock
tRRD = Auto
tRC = 22
tWR; tWTR; tREF; tRD; tRFC and Asynch latency all set to Auto

Would I see any performance increase by purchasing CAS4 ram? If so, what would be a good ram to buy?

Does EPP have advantage in my MB (automatic settings/configuration)?

Is there any benefit to purchase higher mem spec (i.e. 1066) and run at 800 inm this MB? Or should I just leave this alone and stay with current:

IMO, save your money and time. The core 2 isn't that sensitive to the RAM bandwidth. If you want to play you could tighten your timings a little, but you probably won't notice it.

The only performance increase you'll see is in a benchmark, the c2d has excellent prefetchers

Thanks for the info. I will stay with current setup.

If you upgrade RAM, do get more RAM, speeds and timings do very little.