'Using a quad-core' is not of much help regarding Sins, as it is a single-threaded game. CPU speed is the important factor. As long as you have at least 4GB RAM, so that the game can use 2GB and leave the other 2+ for the OS.
As said before, a huge map with thousands of ships per player puts a lot of pressure on the CPU. Good excuse for that Ivy Bridge goodness.
I wonder what are the graphics settings to make Sins playable on the Intel HD 4000 GPU?