yea no point buying X58 1336 as its EOL,
1155 2600k if you need the threads but if your smart 2500k + Z68 can be had for at least USD wise $229 + $149 add in 8gigs DDR3 1600 for $45 = $423
So 2500k + Z68 + 8gb DDR3 = $423 usd
i7 960 + x58 + 6gb DDR3 = $540 usd
$120 more for less performance in Shogun 2,
its not just CPU speed or cores overall memory bandwidth matters in games with high end gpus
example 1600mhz DDR3 triple channel on X58 is SLOWER then 1333 Dual Channel on P67 / Z68 1155 setups some of the mainstream X58 builds i see hitting 18gb/s bandwidth p67 with stock ram stock cpu i get upwards of 22gb/s overclocking the cpu go me up to 24gb/s with dual channel ram thats cheaper. its a whole package situation
Architecture wise 1155 has better IPC aka better per clock performance then i7 1336 cpus has a better IMC in terms of bandwidth, runs a

ton cooler,
a 2500k at 4.5-4.6ghz can be done with a standard air cooler on an i7 1336 platform youll top out at 3.8-4ghz the extra threads on the i7 help but are worthless in games so the cheaper cooler running 2500k will go further and play games better overall then a 1336 based system
better off starting with
http://bit.ly/qYNoFK
or
http://bit.ly/nkA9sH
i went with Link #2 the i30 system and just added what was neccesary.
select the 2500k but DO NOT select the P67 sabertooth, if your system isnt setup properly the sabertooth boards run to hot causing issues depending on case airflow due to the stupid plastic armor

they put on the motherboard
either of those systems fully tricked out will be better for total war then the i7 system your looking at
fully setup i picked
Crucial 8gig 1333 cl9 kit will give you around 19gb/s memory bandwidth
2500k - for gaming no point in 4c /8t 2600k if the 2600k was real 8 cores id consider it but its not so 2500k it is
750TX psu - non modular but solid all the same will get the job done
6950 2gb - AMD gpus are well known to out pace nvidia in shogun 2, where 2x 6950 2gb gpus beat 2x 580s with relative ease
msi p67 GD 65 - does the job has better bios then gigabyte boards no

plastic armor like the sabertooth
darkfleet case
crucial m4 128gb SSD
Western Digital 1tb Caviar Black HDD
need more performance buy another 6950 2gb later and crossfire it with the other card, eitherway thats what i would pick that and get a better cooler for the CPU, so it can be overclocked
total cost on komplett for what i picked out above is 13400 half the price of what you were looking at