"Standard" that came with the case is a very doubtful "standard". Since the cards recommended PSU is 400 Watts....You can give it a try with your current PSU and put it through a few stress tests and see if it works fine.
If not, then you'll know if you need a new PSU or not.
Adding RAM in a rig that has insufficient power is not going to help it work.
First see to it that the PSU works fine for your rig with the GPU and then if it does, go for the RAM.
Can you please give me a program to test my GPU?
It will work.. have you already bought them?
Nope not yet , thats why i asked her first so i don't regret buying anything