core I3 2100 dual core - Best gpu to use
What would be the best graphics card tp put into a i3 2100 dual core pc for hashing... and wpa

i was thinking of putting a GeForce GTX 1050 into play 
or a radeon rx280x . i would prefare the radeon r280x as iv heard its alot better than most , on prices.

Would anybody advise me against this . And if so what are the pro's / cons

I expect power consumption to be mentioned....

But iv also heard that any graphics card would work with the i3..

So what would be the best for my setup. power supply is a 350w at mo..

Any advice would be of use, thank you.

i3 pc specs

intel core i3 2100 3.1ghz
OPENCL upto 4.1
4 gb ram
64bit op
windows 10 (64bit  1079 build)

16x slot 
Bump it up.
The CPU is fine. But your PSU is not powerful enough for a Radeon 280x. That beast alone can draw ~300W under hashcat and would burn a 350W power supply almost instantly.

If you're on a budget, try getting a GTX960. Or even a 970. Even the latter stays well under 200W if you don't overclock it.
Thanks for the heads up... 

how do i compute watt sort of wattage i need for specific craphics cards.... 

is it a spec of the graphic card anyway... as in the graphics card specs will state that it requires a 350watt or a 400watt. or do i have do some groundwork to figure out what wattage i require.. 

But thanks for the advice.., i would of burned the flat down otherwise "lol"
If it’s a higher end AMD card, you’re usually safe guessing 300W+. My R9 290 drew a little over 300 and my R9 390X pair drew around 350W each. Got rid of those within a few days. Nvidia says their power requirements on their website and are usually quite accurate at stock clocks.
The key is the 12V-line on your PSU. It should have the necessary GPU power plus 50% safety margin. The GPU power is defined by its TDP. If you don't tweak with it that's pretty accurate - at least for NVidia cards.

The TDP for a GTX960 is 120W, GTX970 -> 145W, GTX980 -> 165W.

A problem are the power peaks, which can draw up to 50% of the original TDP for a short time.
That is why you need enough power headroom.