No.
It will give you a good increase in very high res/quality settings, and dependant on game, but nothing near double.
If you had a 200HP car that could do 0-60 in 6 seconds, and a top speed of 150 mph, dropping a 400HP engine in it wouldn't give you a 0-60 of 3 seconds and 300 mph either .. double the power hardly ever means double the performance in most situations.
Certainly not good value for money, but then thats not what the question was
Nor is getting hammered a few nights a week with only a hangover to show for it, but many do, now If I could have 12 hangovers or one piece of top end hardware ..... I think you know were I am going