I have a Dell Optiplex 7010 SSF, Corei7 3770 - 6 GB ram - power supply 240W

I want to know What is the highest Vega Card Compatible with it? 
I want to run high graphics games like Assassins Creed: Syndicate, So i want to buy Nvidia GeForce GTX 760 or GeForce GTX 660, AMD Radeon R9 270 Or Radeon HD 7870 or something else , but
Someone told me, Not all graphics cards work with you, It's about what is compatible with your device, motherboard, your power supply and what can be carried , Modern graphics cards are working on 600W or higher power supply and your power supply working on 240W so you have no chance to run these cards on your computer
and too your device is compatible with "Mini" graphics card only.
So  can i know what graphics cards can i run with my power supply or my device.
Thanks a lot :)