windowsdownsystemup
it's been a long time, however I have solved the issue. Somehow, since installing my GTX 1080 FTW, the CPU only used 1 or 2 cores (it's been a while since I got it working, so I can't remember how many exactly), which wasn't an issue when I had my prior card installed, and was only happening in source enginge games. So forcing the use of the correct amount of cores through windows solved all my problems, the game now runs (at 1280x960) at 600-1100 fps, as you would assume from such a setup. I had to cap it under 999, since the game started stuttering like mad when going above.
To all of you who say there is no difference between consistent 144 fps and ~300 fps, I will assume you are not CS:GO players. The difference in fluidity is very apparent on a 144hz monitor which is, I assume, is due to better frame time. Above ~300 I cannot tell a difference. Once again, this is exclusive to source engine games. In other games I am very happy with 144 FPS, and cannot feel a difference when going above it. The lack of fluidity in CS:GO at 144 FPS does not feel like it is tied to the refresh rate, since the 'stuttering' is very inconsistent when compared to, let's say Mafia 3 @ 30 FPS.
 
Anyway, thank you for your help and suggestions.

windowsdownsystemup
it's been a long time, however I have solved the issue. Somehow, since installing my GTX 1080 FTW, the CPU only used 1 or 2 cores (it's been a while since I got it working, so I can't remember how many exactly), which wasn't an issue when I had my prior card installed, and was only happening in source enginge games. So forcing the use of the correct amount of cores through windows solved all my problems, the game now runs (at 1280x960) at 600-1100 fps, as you would assume from such a setup. I had to cap it under 999, since the game started stuttering like mad when going above.
To all of you who say there is no difference between consistent 144 fps and ~300 fps, I will assume you are not CS:GO players. The difference in fluidity is very apparent on a 144hz monitor which is, I assume, is due to better frame time. Above ~300 I cannot tell a difference. Once again, this is exclusive to source engine games. In other games I am very happy with 144 FPS, and cannot feel a difference when going above it. The lack of fluidity in CS:GO at 144 FPS does not feel like it is tied to the refresh rate, since the 'stuttering' is very inconsistent when compared to, let's say Mafia 3 @ 30 FPS.
 
Anyway, thank you for your help and suggestions.