It is a KNOWN fact that starcraft 2 requires a minimum of 4.8 GHZ sandybridge, or a 4.5 ghz ivy bridge to Maintain Solid frame rates in Heavy battles.
Also, turning off hyper threading will improve responsiveness in SC2.
In fact, if you can get 5ghz.. that's even better.
Can you link me to benchmarks that show this is true? Most serious starcraft players play 1v1s and maximum supply cap there is 400 so I'm surprised as to why you need such a high clock to get satisfactory frame rates. From this video's benchmarks, they got over 60fps at ultra settings with a 7770 at 1080p no AA. The benchmark was done at more intensive scenarios then a 1v1 match usually is at. This, btw, was on WOL not HOTS.
The 560ti the OP has is a better card than the 7770 yet the point here is that he is getting lag on low/medium settings, which I do not think should be happening. Also, i5 2500k/2550k does not have hyperthreading so he can't turn that off.
I've been following SC2 scene since core 2 and i7 920, we KNEW back in the day of 920 C0 what it would take to have 60fps WORST CASE since SC2 scales linearly with Cpu frequency..
best at that time was 4 - 4.2ghz on the 920 D0 stepping...
Look this is an OLD issue we're talking about here... IDK about this random youtube guru you posted about... anyone serious into SC2 hardware would agree on 4.8ghz sandy, which was the FIRST time we actually crossed the threashold for solid 60fps worst case..
Benches were usually 3v3, this was because otherwise, there'd be too many splotches where frame rates would climb extremely high, thus thwarting the results..
In an RTS, you have to test worst case... because when you have very few units, your fps climbs to 100+, 200+, now if these sections were averaged into the benchmarks.. which in a 1v1 would happen,, then you'd come out with something like 70fps average,, when minimum frames could be 24fps...
This is the difference between FPS game testing and RTS.... because in FPS, the game is pulling at a much more consistent rate.
As far as OP's cpu he mentioned something something 23xx 25xx , so I can only assume that He may have a 255k or 25k OR something 23xx, which might have hyper threading.. so I suggested, that turning it off would benefit SC2... simple..