Alienware x51 r2 gpu upgrade

[Xenax]

Ive been looking into buying a gtx 950 for my alien ware x51 r2 that i bought back in December of 2014. I know ew alien ware ew pre built but around black Friday I will be looking into building a new pc with a 1070. So as for my question, is my PSU powerful enough for a gtx 950? I think I have the 240W external psu for my pc but am not sure as some have 180w. As the pc will only be used for a few more months as my main computer and after for LAN parties, I dont want to have to spend more money on upgrading to the psu to the 330w unless necessary. If anyone is able to give me answers id appreciate it or any other gpu recommendations (the 950s ive been seeing are around 75-85 USD i dont want to go higher than that unless the other recommendation is more expensive but will not require a psu upgrade). Thank you and here is my current specs.

gtx 745   4GB

6gb ram 1330MHz

i3 4150 3.5GHz

1TB HDD

240w external psu (or 180w not sure)

 

[Droidbot]

1050 has lower power usage and very very slightly higher performance. 

 

Have a look for them.