PCIe x1 CARDS IN A PCIe x16 SOCKET

maybe u could consider msi mobo's...
790FX-GD70
K9A2 Platinum
K9A2 Platinum V2

the K9A2 Platinum looks my best option, but only if i can use the other 2 PCIe x16 slots for PCIe x1 network cards and PCIe x1 sound cards without effecting the x16/x16 crossfirex... can i do this?

i really dont know about that. have u review the mobo here?
http://asia.msi.com/index.php?func=proddesc&maincat_no=...
r u building a new rig, or upgrading an existing one?

I don't know. It says Dual 16x, 16x/8x/8x, or quad 8x. That probably means the slots share lanes ... so there would be a total of 32 lanes available for all four slots. If that's the case, it would mean yes, having anything in the third and fourth slots would take away from what's available to the video cards.

Personally, I'd ditch the PCIe x1 network card for a regular PCI version (which is still going to be plenty of bandwidth for an Internet connection) and then see if there's a board like this that you can shoehorn everything into where the dual x16 slots are independent from everything else.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

IM UPGRADING AN EXISTING ONE BUT I WANT TO STICK WITH DDR2. MY CURRENT SYSTEM IS...

ASUS M3N78-VM MOBO
AMD PHENOM X4 9550 (2.2GHz)
4GB KINGSTON DDR2-800 CL5
500GB 7200RPM DRIVE
PALIT GEFORCE 9600 SMART 1GB

... BASICALLY I WANT A DUAL CROSSFIREX MOTHERBOARD WITH ROOM FOR 2 FULL SIZE GRAPHICS CARDS, PCIE X1 SOUND CARD AND A WIRELESS NETWORK CARD. I DONT HAVE A LOT OF MONEY SO I WOULD LIKE TO BUILD BIT BY BIT STARTING WITH THE MOTHERBOARD!!!  

oic... 2 full size gc means like ati5850 or nvidia260 and above rite? that would be nice...  
ok, i think, if u install pcie x1 sound card, it wont effect the bandwidth of the two pcie x16 slots where u put on ur gc... no worries bro, u will still getting the best out of ur crossfirex,just dont use the other two pcie slots. plus, the wireless network card would be install into the pci slot isnt it?  
(i'm referring to the msi mobo. there's other mobo Asus M3A32-MVP Deluxe/WiFi-AP, which already has wifi adapter)