Game lags a lot

I have a hard time playing the game in its current state. I tried playing with the default options at first and everything in the game was lagging, even the main menu. Now I play with minimum resolution, low quality, DirectX 9, windowed. This helps a little (even though the text becomes almost impossible to read) but as soon as my base has more than 3 or 4 buildings, the game starts lagging massively. Every hover takes about 1 to 2 sec to show up. Sometimes I see the hover box get "constructed" with text changing after a couple of frames. When I want to buy or sell stock, it takes about 1 second to register a click and then another 1 or 2 seconds for the "ca-ching" sound to play and the money to pop up. The black market is even worse and after a while I just quit the game because it becomes unplayable. Upgrading a technology or getting a new patent is a no-no because opening the menu for that will freeze the game for about 3-5 seconds, same when closing the menu.

I have a little bit more than the minimum requirements. My graphics drivers are fully updated with fresh install to make sure.

OS: Windows 7 64-bit

CPU: Core 2 Duo 3.2GHz

RAM: 8 GB

GPU: Nvidia GTX 480 4GB

 

I really want to enjoy this game but right now it's just not playable for me and I feel like I wasted 35$... I had to think a long time before shelling out the money for this because I'm currently on a very tight budget and this is the only game I can buy in the next 6 months, and right now I can't even enjoy it. I hope you guys can fix that or at least crank up the minimum requirements so others who think they can run it won't feel burned by their purchase.