Stuttering impossible to fix

Semeds98

Reputable
Aug 23, 2014
2
0
4,510
Hi everyone (new member incoming), It's been a year since I experienced troubles with stuttering and related issues.
I can't find a way to solve this, really.
I'm stuttering in many games, such as Left 4 Dead 2 (that's the biggest problem, stuttering there is AWKWARD), Mortal Kombat 9 (during cutscenes), Bioshock (not that much but still notable), ecc...
I'm also not running very smoothly lite client-based games.
Specs: previously FX-8320+Sabertooth 990FX+H80i+R9 280X Toxic+XFX 850W, now i5 4670+GA-H87-HD3+H80i+R9 280X Toxic+AX1200 (I've borrowed these parts to test the system and find a way out of stuttering).
Here's what I tried:
Replacing Monitor: 3 times, nothing.
Replacing GPU: replaced my R9 280X Toxic with i5 4670 GPU and R9 270X Dual-X (my old video card. When I purchased it first everything worked like a charm, more or less. Still better than now).
Replacing HDD: about 3 times, I tried with a Barracuda 1TB, Caviar Blue 1TB and Hyperx 3K SSD.
Replacing Motherboard: I used a Sabertooth 990FX, now I've passed to a GA-H87-HD3 but still nothing.
Replacing CPU: as I replaced the motherboard with a different socket I also changed CPU (FX to i5).
Replacing PSU: I've used an XFX 850W XXX, now I've upgraded to an AX1200 (for future upgrades too).
Replacing RAM: about 5 times, tried with different Vengeance Sticks.
THERE'S NO POINT, cause a PC I've made out of my spare parts (i5 650, P7P55D Deluxe, XFX 450W, Palit GTX 560 Ti) also stutters but much less than the other one. Client-based low-end games (I like NosTale. It's cute lol) run pretty smoothly.
I forgot to say I own an original copy of Windows 7. Where am I mistaking?
World hates me.
Thanks...