Budget Gaming PC Urgent!

[SuperCalifornialific]

I'd like to game and play pretty much last generation titles, along with MOBA's and most Steam games. I'd like to be able to run Batman: Arkham Origins at a solid 60 FPS with a decent resolution. Can you guys whip me up a system under 400? A system that is upgrade-able and can be built into a beast when I have money? Thank you.

No OS nor anything other than the pure components are needed.

 

[3Dns]

I did my best...

PCPartPicker part list / Price breakdown by merchant

CPU: AMD Athlon X4 750K 3.4GHz Quad-Core Processor ($79.49 @ OutletPC)
Motherboard: ASRock FM2A75M Pro4+ Micro ATX FM2+ Motherboard ($59.49 @ Newegg)
Memory: Kingston Fury Red Series 8GB (2 x 4GB) DDR3-1866 Memory ($72.99 @ Amazon)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: EVGA GeForce GTX 750 Ti 2GB Superclocked Video Card ($129.99 @ Newegg)
Case: NZXT Gamma Classic (Black) ATX Mid Tower Case ($19.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($25.99 @ Newegg)
Total: $437.93
Prices include shipping, taxes, and discounts when available

 

[Danbuscus25]

PCPartPicker part list / Price breakdown by merchant

CPU: AMD A10-7850K 3.7GHz Quad-Core Processor ($169.96 @ OutletPC)
Motherboard: ASRock FM2A75M Pro4+ Micro ATX FM2+ Motherboard ($59.49 @ Newegg)
Memory: G.Skill Trident X Series 8GB (2 x 4GB) DDR3-2400 Memory ($72.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($54.98 @ OutletPC)
Case: NZXT Gamma Classic (Black) ATX Mid Tower Case ($19.99 @ Newegg)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($25.99 @ Newegg)
Total: $403.40
Prices include shipping, taxes, and discounts when available

this is the best you can get, but it will not run games at very high settings. as far as upgradability, you can add a low-end amd card and run it in dual graphics mode with the apu.