aren’t 8gb enough anymore?^^ I bought this pc at least 4 years ago…
could possibly be that it has more, but at least 550W
8GB should be enough. On my rig the game uses around 5GB alone, so if you don’t have 30 tabs in Chrome open, no problem. More important than the sheer Watts are the A on the +12V rail(s). If it isn’t a problem for you, you could post those here, they’re located at the side of your PSU. Unfortunately there are huge differences between noname and brands.
I would rather wait for gtx960 release. 200 euros for gtx760 isn’t really worth it, as you can get gtx970 already for 340 euros.