If you can wait several months and lowest cost gaming is really what you want to achieve I think AMD Trinity A10-5800K or A10-5700 might do the job.
It will be fine for Portal and sims 3, and can just about manage BF3.
Here are benches for the mobile part which the desktop part will easily best.
http://www.anandtech.com/show/5831/a...m-a-new-hope/6
AMD Llano A8-3870K (top APU from current gen) is ~$120 it would not be unreasonable to presume the A10-5800K coming out around the same price.
That would save you $120 compared to the i3 + GTX460 combo.
It looks like it is now delayed until Sep/Nov so if you needed it sooner you are out of luck.