Depends on whether or not the graphics card you plan to SLI/Crossfire are high end or mid-range. For your task I recommend 880, however if you plan to use high-end cards I would recommend the 950 simply because it can provide the cards with the bandwith they need.
Bandwidth isn't really a problem, since there really ins't much of a difference between 8x/8x and 16x/16x (*check this site for more info: http://hardocp.com/article/2010/08/23/gtx_480_sli_pcie_...). However, for your graphic designs, the 1366 socket can utilize more memory. If your applications aren't too system-intensive, I'd go for the 880 purely since the subsequent hardware is so much cheaper.
Either will do the job, but one or both may well be overkill.
Can you tell us your screen resolution (eg, 1920 x 1200)? Are you a serious or casual gamer, eg, do you game a lot? or occasionally? How important is it that you can play "at max settings"?
Finally do you do a lot of graphics design? Or, since you listed it third, just occasional? Would you want to spend more than normal amounts of money for smalller than normal improvements in performance in that application?
well currently im using 1680 x 1050, i'm a serious gamer but i shared my gaming time between PC & PS3, would love to play at max settings if i could but i guess i would be happy with a step under max settings.
graphic designs - would be using softwares like photoshops, illustrators, lightroom.
from history i dont tend to upgrade my machine, for the ones i did it was just memory/hdd.
But would it be better to go with the 950 and perhaps when the 6-core gets cheaper i could upgrade to that?
Two things you have to consider - power consumption and price.LGA 1156 mobo+ i7 880+Ram will be cheaper than LGA 1366+ i7 950 + RAM and it will consume less power as well.Performance will be nearly equal.I do not think that current 6 core Intel CPUs will get cheaper any time soon.So i7 880 seems to be a better choice.
You don't need the expense, power requirements, and heat of the 950 for outstanding gaming at 1680 . . . or even at 1920 for that matter.
The 8XXs give you four cores and 8 threads. But most of your uses will not make use of them. Games, eg, pretty much top out when given 3 cores. Multi-tasking would make use of the cores/threads.
For the same reasons, 6-core processors are not likely to be better for your uses. Especially since "inexpensive" ones are likely to have lower clock speeds than the quads. That could lower your performance in games while improving multi-tasking speeds and perhaps some graphics applications.
There's nothing wrong with either 9XX or 8XX systems, but a 7XX system can be considered if you want to save $100 to $250 and get comparable performance. Your uses aren't that demanding.
An i5 750/GTX460 system for gaming at 1920 will cost around $950 (just the tower). That system would be very satisfying for your uses for quite some time. If you know you are staying at 1680 resolution, you can shave ~$70 off by stepping down to an appropriate ATI card.