Depends on the CPU you are using, if it's a good cpu then you should get 150fps on dust2 and mirage for sure.
Keep it like that and if it lags then you should upgrade it. Get the 144HZ monitor first though
deffo over 150, i have a shitty i3 and a gt640 and a year ago i was getting around 200, now 150
I have a 750 Ti and get around 75-140 FPS depending on the map. Then again, my CPU is pretty bad for CS:GO and that's the reason why I have such low FPS. If you get a decent CPU, you can use the 144 Hz monitor with no problems whatsoever. I currently have a 60 Hz monitor and play 4:3 so I can get to 75 Hz. My CPU is an AMD A8-6500 if you're interested in what it currently is. Good luck!
EDIT: Sorry, I didn't see the CPU in the post. You should definitely get the 144 Hz monitor, you won't regret it.
thanks guys, helped a lot <3
Remember that scaling your resolution and settings is always an option, if you put your stuff on low you should be able to get more than 150 fps I would expect.
750Ti + i3 4170 + 8gb ddr3 = 250+ fps. If you buy a better cpu, then I guess you'll get more fps.
Cs depends a lot on the CPU, your CPU is good, you should probably get an average of 250 fps playing in 1280x960 or lower, not sure on 1920x1080.