The i7 is a quad core.
Yeah, if I were you I'd just save up for a new system and use what you've got for right now.
Everything is differnt now. Computers are now using DDR3 memory. Your whole setup is in need of a face lift. Your video card is okay, but it isn't good enough for using higher settings in the newer games. When you do get ready to get one, I'd stay away from the name brand ones like HP, Dell, and etc. Go to your local dealer and get one built or build it yourself. That way it makes it easier to upgrade things and keep up with the advances that come along.
Take care, and happy gaming!