im specifically looking at the first and second choices. is it worth the extra $100 for the i7 2670QM? it tops out at only 0,1GHz higher, but can also be 0.2 GHz lower then the i5 so on average, the i5 is faster. when does cache come into play? the machine will mainly be used for light-medium gaming. will the extra 3MB cache be worth it to me?
The biggest difference between the i5-2430M and the i7-2670QM is that all i7 with the "QM" designation are quad cores. Al mobile Core i3 and i5 CPUs are only dual cores. For games, the cache does not make much of a difference. For games that can take advantage of more than 2 cores, the performance will be better with the i7. However, most games still only use dual cores.
I would go with the i5-2430M and use the extra $100 towards a graphics card upgrade which can prolong the life of the laptop for gaming purposes.