first of all: what are your ragdoll and corpses settings?
set these to like 15 each and try a strat battle
also set shadows and shader to something like medium or low
is that your current setup or a "i might buy that one" setup?
if its your current one then the lag must have other causes
if its not your current one, can you post yours?
cause maybe you dont need to spend so much money, renewing a few parts rather than a whole new pc might be sufficient too
and there is absolutely no need for a SSD if you think about getting that posted rig, 16gb RAM will run fast as hell
RAM is very important though
my friend has a slower cpu, much worse graphics card, slower HDD but 8gb RAM, while i have only 4gb RAM, and his PC runs quite a bit faster than mine
(a total war rome2 battle loads about twice as fast for him than for me at the same settings)
ASUS M4A87TD EVO
AMD Phenom(tm) II X4 955 Processor, MMX, 3DNow (4 CPUs), ~3.2GHz
4092MB RAM
250 GB HDD
1TB External HDD
NVIDIA GeForce GTX 660 2048MB GDDR5
and i run a constant 120fps at almost max graphics (corpses to 25 and shader to the medium-setting)
smoke bombs do nothing to my fps (maybe if there are like 5 at the same time next to me, but so far i never noticed an FPS drop