Whats hindering you right now is the I3 and the integrated graphics. Bumping up into the i7 quad-core processors is going to fix your problems. Make sure you get a machine with dedicated gpu memory. I run the game on high and it is silky smooth. Here is what i have for comparison.
ASUS
i7 2.20 GHz
8GB RAM
750 HDD
GT 550M 2GB