The 965 is faster at stock speeds. However, it's the same physical chip as the 955. That means you can save some money, buy the X4 955 and apply a slight overclock and have the same thing as the 965. You don't even need an aftermarket cooler to get the same speeds.
Also, the 790FXTA-UD5 is NOT the latest. Any of the 890GX boards are the newest AM3 CPUs, and the only difference with the 890 chipset is they won't need a BIOS update to use the upcoming six core CPUs.
The differences betwen the UD4 and UD5 are:
UD5 has an extra PCIe 2.0 slot, which doesn't do anything as Crossfire doesn't scale well past two cards.
UD5 has 16x/16x on the first/second slots, which is only a 4% performance gain over 8x/8x and only noticeable with HD 5970s
UD5 has two exta USB 2.0 ports in the back
UD5 is $55 more expensive
So basically, you're paying $55 more and not getting anything for it.
If you get the 955, get the C3 chip not the C2 chip. Even so, remember that a 955BE C3 is a chip that didn't cut it to be a 965BE running at default voltage. As long as you have a good cooler though, the general difference in their over clocking ability is small. Of course, it all depends on your particular sample how far you get .
Yeah no real point to get the 965, but if you insist just go with it. If you do choose to get the 955 remember what megadmanx00 said and make sure you get the C3 stepping version. the product number will end in MBOX if it's C3. Also if you don't want to overclock the 955 I'd advise going into bios and lowering the stock voltage. The 955 comes stock at 1.4v i think but i run mine at 1.32(or something around there) and it runs a lot cooler(been running like that for 1-2months and no problems, but not needed if you use an aftermarket cooler which i dont, yet.). As for the motherboard I'd suggest the GIGABYTE GA-890GPA-UD3H. Newest chip set and a bit cheaper. It runs magnificently.
GIGABYTE GA-890GPA-UD3H OK.SAW THAT on net.would it be enough for downloading ,surfing ,high end games,dolyby surround music
.. want to ensure that i would not upgrade y pc for atleast 3 years would all the combinations work ok . i mean the cpu 965-125w,GIGABYTE GA-890GPA-UD3H motherboard , ram and sapphire 5850 , and corsair psu... what abt the case cooler master 690 advanced 2..