[Build Help] What's the cheapest single GPU I could buy that would be better than my 7870s running in crossfire?

Part Price
CPU i3-6100 3.7GHz Dual-Core Processor $108.99
CPU COOLER Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler $29.88
Motherboard MSI H110M Gaming Micro ATX LGA1151 Motherboard $69.88
RAM Crucial 8GB (2 x 4GB) DDR4-2133 Memory $47.99
Storage Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive $49.78
Video Card Zotac GeForce GTX 750 Ti 2GB Video Card $130.50
Case NZXT S340 Elite (Black) ATX Mid Tower Case $89.99
Case Fans Thermaltake Riing 14 LED Red 51.1 CFM 140mm Fan (x3, 2 intake, 1 exhaust + 1 exhaust that comes with case) $16.89
PSU Corsair Builder 500W 80+ Bronze Certified ATX Power Supply $46.99
OS Microsoft Windows 10 Home OEM 64-bit $88.58
Total: $713.24

This is my first time building a PC. I just had some questions concerning performance, compatibility, and overall suggestions.

I'm on a fairly low budget, so my build is a pretty entry-level build (which I'm fine with). I was planning on only spending about $620, but I forgot about the case fans and ended up upgrading the case. If you have any piece swapping suggestions, I just ask that it won't bring the price over $740.

The games I will be playing include League of Legends, Overwatch, Minecraft, CS:GO. Obviously won't be playing anything in 1440p because this rig won't be able handle it with my budget. Will this PC be able to run those games in 1080p, max graphics, 90-120+ fps? I might end up buying some newer games on Steam and I was wondering if it would be possible for me to run mid-low settings to get a steady 60 fps for 2016-17 games? I hope what I'm aiming for isn't too far-fetched for my budget. I'd also like to use some shader packs for Minecraft. Would 60fps with a nice shader pack be unrealistic?

Will these pieces be compatible? I used PC Part Picker (which I'm having a hard time trusting), and it said everything was compatible, but I'm also wondering about the assembly. Will the case be okay with the pieces I bought? This feels like a dumb question, but the motherboard model includes the word Micro. So I was wondering if that means it would be smaller? Will it leave the case looking really empty, or even be able to mount onto the case considering it's size?

Is a 500W PSU enough? Am I spending the right amount of money on the right pieces? Am I overspending on something unnecessary? Do you have any better suggestions that will noticeably improve performance without breaking the budget?

Thanks for your time :)

/r/buildapc Thread