It is true that the i7 is a superior chip, the difference in gaming is not great. The advantage of the i7, as others have said, lies in CPU intensive tasks such as video encoding. Also I prefer AMD as a company to Intel, seeing as they run events such as this:
which while incredibly impractical in real life is cool. Yes it has been topped by later i7 chips, but these are from chips that originally shipped in April of 2009. AMD come across as a fun company where as Intel are more like bankers.
Pre-order bonuses should be just that. I really like what has been done with steam on occasion, pre-ordering a game gives you a discount as well as another full game. Most pre-order bonuses are simple reskins of models, or an extra vehicle. A preorder containing an extra quest or mission is not so great. At this point I would say the free DLC for original buyers is the best approach ala Mass Effect 2, Forza 3, etc.
The rationale behind pre-order bonuses however is sound, if you are willing to pay full price on or prior to day one then that is generally better for everyone in the industry. If purchasing at a later date one can often find the product for a lower price. Maybe a first week purchase with the bonus, then said bonus being released for a small fee later down the line would be a possible solution.