I would start with pulling the head. IF the broken timing belt hurt the pistons at all, you will see it in the cylinder with the head off.. If you are doing the work yourself, pulling the head is free.

AND if you are capable, you can replace, and lap the new valves yourself (provided the head is ok which you will know when you pull it). This would cost you about $200-300 depending on how many valves you need.

the ecotec Cobalt stuff is a tough fit, but the 1.4t, and 1.8 in the cruze and sonic fit..