If planning on overclocking, I would get the 1055T. You should be able to reach close to the same clockspeeds as the X4 980 and you get two extra cores. But it will take some more effort to OC, as it's multiplier-locked.
At stock, the clock speed of the 1055T is a bit low at 2.8 GHz, and Turbo Core only increases that to 3.3 GHz, when three or fewer cores are being used.
Don't worry about the life span of the CPU. Five years from now, you can probably find used Phenom II CPUs virtually for free.
Another option is to get an i3 now to compensate for the more expensive Intel motherboards, then buy a used or new i5-class CPU down the road. Keep in mind that an i5 running at 3.5 - 4 GHz will be significantly faster than anything you can get from AMD.