Hello,
 
I'm building a new system, but I'm still trying to decide which motherboard I should use.
 
I want to buy a quad-core cpu Q6600 but I don't want to spend on DDR3 mem so I want a motherboard that handles DDR2 and DDR3 so I would be able to upgrade later.
 
Also I will build a crossfire connection using 02 HD2600 video cards so it has to have 02 PCIe slots.
 
I was looking into Asus, Gigabyte and Intel boards but now I'm so confused that I don't know which one should I get it. Also could someone tell me if a crossfire connection with 02 HD2600 512MB DDR3 will worth it or should I get another card...?
 
ASUS P5KC ; P5kE; P5E3
Gigabyte GA-P35C-DS3R; GA-EP35-DS3P  
Intel DP35DPM
 
Any advise...???  
 
Thanks

If you're xfiring look at the X38 boards.

consider Foxconn's x38a:

http://www.newegg.com/Product/Prod [...] 6813186134

Don't do Crossfire with 2 weak cards, You will be much happier with a single HD 3870. Also, if you get an X38 motherboard (GA-X38-DS4 is my favorite) you will be able to add a second HD 3870 later when you need it. All but one of the boards you listed are based on P35. Most are very good, but all of them are bad choices for Crossfire because the P35 chipset cannot offer x16 speed to both video cards. The GA-P35C-DS3R doesn't even have a physical slot for a second video card.
 
Don't worry about DDR3. Motherboards with dual support for DDR2 and DDR3 tend to overclock less well (example my own GA-P35C-DS3R compared to GA-P35-DS3R which doesn't support DDR3 and costs less and overclocks better). By the time DDR3 is worth buying you will want a Nehalem CPU too, and those won't work on the LGA775 motherboards you can buy today.